Topic 3: MC

Question No : 172 - Topic 3 Which address is a MAC address that is mapped from an IPv6 address (RFC 2464)? A. 3333.FF17.FC0F B. FFFE. FF17.FC0F C. FF34.3333.FF17 D. FF7E.FF17.FC0F question_answerVIEW ANSWER

Answer : A Explanation: An IPv6 packet with a multicast destination address DST, consisting of the sixteen octets DST through DST, is transmitted to the Ethernet multicast address whose first two octets are the value 3333 hexadecimal and whose last four octets are the last four octets of DST. Reference: https://tools.ietf.org/html/rfc2464

Question No : 211 - Topic 3 Which statement describes the function of the tracking object created by the track 10 ip route 192.168.99.0/24 reachability command? A. It tracks the reachability of route 192.168.99.0/24. B. It tracks the line protocol status of the interface on which route 192.168.99.0/24 is received. C. It tracks exactly 10 occurrences of route 192.168.99.0/24. D. It tracks the summary route 192.168.99.0/24 and all routes contained within.

Answer : A Explanation: Command Purpose Step 1 configure terminal Enter global configuration mode. Step 2 {metric threshold | reachability} | list {boolean {and | or}} | { threshold {weight | percentage}}} (Optional) Create a tracking list to track the configured state and enter tracking configuration mode. range is from 1 to 500. to select an interface to track. Enter line-protocol to track the interface line protocol state or enter ip routing to track the interface IP routing state. to track the state of an IP route. Enter metric threshold to track the threshold metric or enter reachability to track if the route is reachable. The default up threshold is 254 and the default down threshold is 255. Enter list to track objects grouped in a list. Configure the list as described on the previous pages. Note Repeat this step for each interface to be tracked. Reference: http://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3560/software/release/12- 2_52_se/configuration/guide/3560scg/sweot.html

Question No : 244 - Topic 3 Which multicast protocol uses source trees and RPF? A. DVMRP B. PIM sparse mode C. CBT D. mOSPF

Answer : A Explanation: DVMRP builds a parent-child database using a constrained multicast model to build a forwarding tree rooted at the source of the multicast packets. Multicast packets are initially flooded down this source tree. If redundant paths are on the source tree, packets are not forwarded along those paths. Forwarding occurs until prune messages are received on those parent-child links, which further constrains the broadcast of multicast packets. Reference: DVMRP and dense-mode PIM use only source trees and use RPF as previously described. Reference: http://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3550/software/release/12- 1_19_ea1/configuration/guide/3550scg/swmcast.html

Question No : 232 - Topic 3 Which BGP aggregate address configuration advertises only the aggregate address, with attributes inherited from the more specific routes? A. summary-only as-set B. as-set C. summary D. summary-only

Answer : A Explanation: Example: router bgp 300 neighbor 2.2.2.2 remote-as 100 neighbor 3.3.3.3 remote-as 200 neighbor 4.4.4.4 remote-as 400 aggregate-address 160.0.0.0 255.0.0.0 summary-only as-set Reference: http://www.cisco.com/c/en/us/support/docs/ip/border-gateway-protocol- bgp/5441-aggregation.html

Question No : 274 - Topic 3 How does EIGRP derive the metric for manual summary routes? A. It uses the best composite metric of any component route in the topology table. B. It uses the worst composite metric of any component route in the topology table. C. It uses the best metric vectors of all component routes in the topology table. D. It uses the worst metric vectors of all component routes in the topology table. question_answerVIEW ANSWER SHOW COMMENTS 0

Answer : A Explanation: For example if your router has a routing table like this: D 192.168.8.0/24 [90/2632528] via 192.168.0.1, 00:00:12, Serial0/0 D 192.168.9.0/24 [90/2323456] via 192.168.0.1, 00:00:12, Serial0/0 D 192.168.10.0/24 [90/2195456] via 192.168.0.1, 00:00:12, Serial0/0 D 192.168.11.0/24 [90/2323456] via 192.168.0.1, 00:00:12, Serial0/0 Now suppose you want to manually summarize all the routes above, you can use this command (on the router that advertised these routes to our router): Router(config-if)#ip summary-address eigrp 1 192.168.8.0 255.255.248.0 After that the routing table of your router will look like this: D 192.168.8.0/21 [90/2195456] via 192.168.0.1, 00:01:42, Serial0/0 And we can see the manual summary route takes the smallest metric of the specific routes.

Question No : 151 - Topic 3 Which neighbor-discovery message type is used to verify connectivity to a neighbor when the link-layer address of the neighbor is known? A. neighbor solicitation B. neighbor advertisement C. router advertisement D. router solicitation

Answer : A Explanation: IPv6 Neighbor Solicitation Message A value of 135 in the Type field of the ICMP packet header identifies a neighbor solicitation message. Neighbor solicitation messages are sent on the local link when a node wants to determine the link-layer address of another node on the same local link (see the figure below). When a node wants to determine the link-layer address of another node, the source address in a neighbor solicitation message is the IPv6 address of the node sending the neighbor solicitation message. The destination address in the neighbor solicitation message is the solicited-node multicast address that corresponds to the IPv6 address of the destination node. The neighbor solicitation message also includes the link-layer address of the source node. Figure 1. IPv6 Neighbor Discovery: Neighbor Solicitation Message Reference: http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/ipv6_basic/configuration/xe- 3s/ip6b-xe-3s-book/ip6-neighb-disc-xe.html

Question No : 213 - Topic 3 You are implementing new addressing with EIGRP routing and must use secondary addresses, which are missing from the routing table. Which action is the most efficient solution to the problem? A. Disable split-horizon on the interfaces with secondary addresses. B. Disable split-horizon inside the EIGRP process on the router with the secondary interface addresses. C. Add additional router interfaces and move the secondary addresses to the new interfaces. D. Use a different routing protocol and redistribute the routes between EIGRP and the new protocol.

Answer : A Explanation: Normally, routers that are connected to broadcast-type IP networks and that use distance- vector routing protocols employ the split horizon mechanism to reduce the possibility of routing loops. Split horizon blocks information about routes from being advertised by a router out of any interface from which that information originated. This behavior usually optimizes communications among multiple routers, particularly when links are broken. However, with nonbroadcast networks, situations can arise for which this behavior is less than ideal. For these situations, you might want to disable split horizon with EIGRP and RIP. If an interface is configured with secondary IP addresses and split horizon is enabled, updates might not be sourced by every secondary address. One routing update is sourced per network number unless split horizon is disabled. Reference: http://www.cisco.com/c/en/us/td/docs/ios/12_2/ip/configuration/guide/fipr_c/1cfrip.html

Question No : 162 - Topic 3 Where should the passive-interface command be used? A. Under the routing process for interfaces that need to be routed, but prevented from peering B. under the routing process for interfaces that need to be routed and allowed to peer C. under the interface configuration for interfaces that need to be routed, but prevented from peering D. under the interface configuration for interfaces that need to be routed and allowed to peer E. under the VTY configuration within global configuration mode

Answer : A Explanation: Passive-interface is a feature you enable on a per interface basis which allows a particular interface to participate in a routing process but prevents that interface from forming neighbor relationships by not sending hello packets and discarding received hello packets.

Question No : 300 - Topic 3 Which statement about the function of poison reverse in EIGRP is true? A. It tells peers to remove paths that previously might have pointed to this router. B. It tells peers to remove paths to save memory and bandwidth. C. It provides reverse path information for multicast routing. D. It tells peers that a prefix is no longer reachable.

Answer : A Explanation: Poison Reverse in EIGRP states: Once you learn of a route through an interface, advertise it as unreachable back through that same interface. For more information please read here. http://www.cisco.com/c/en/us/support/docs/ip/enhanced-interior-gateway-routing- protocol-eigrp/16406-eigrp-toc.html#splithorizon.

Question No : 164 - Topic 3 Which statement about the RPF interface in a BIDIR-PIM network is true? A. In a BIDIR-PIM network, the RPF interface is always the interface that is used to reach the PIM rendezvous point. B. In a BIDIR-PIM network, the RPF interface can be the interface that is used to reach the PIM rendezvous point or the interface that is used to reach the source. C. In a BIDIR-PIM network, the RPF interface is always the interface that is used to reach the source. D. There is no RPF interface concept in BIDIR-PIM networks.

Answer : A Explanation: RPF stands for "Reverse Path Forwarding". The RPF Interface of a router with respect to an address is the interface that the MRIB indicates should be used to reach that address. In the case of a BIDIR-PIM multicast group, the RPF interface is determined by looking up the Rendezvous Point Address in the MRIB. The RPF information determines the interface of the router that would be used to send packets towards the Rendezvous Point Link for the group. Reference: https://tools.ietf.org/html/rfc5015

Question No : 160 - Topic 3 Which OSPF feature supports LSA rate limiting in milliseconds to provide faster convergence? A. LSA throttling B. incremental SPF C. fast hello D. SPF tuning

Answer : A Explanation: The OSPF Link-State Advertisement (LSA) Throttling feature provides a dynamic mechanism to slow down link-state advertisement (LSA) updates in OSPF during times of network instability. It also allows faster Open Shortest Path First (OSPF) convergence by providing LSA rate limiting in milliseconds. Reference: http://www.cisco.com/c/en/us/td/docs/ios/12_0s/feature/guide/fsolsath.html

Question No : 312 - Topic 3 Which statement about the EIGRP RTO is true? A. It is six times the SRTT. B. It is the time that it normally takes for an update to be received by a peer. C. It is the time that it normally takes to receive a reply to a query. D. It is the average time that it takes for a reliable packet to be acknowledged.

Answer : A Explanation: The RTO is typically six times the SRTT, the value may vary from a minimum of 200 microseconds (ms) to a maximum of 5 seconds (s). Reference: EIGRP for IP: Basic Operation and Configuration, Alvaro Retana, Russ White, Don Slice - 2000

Question No : 255 - Topic 3 Which BGP feature allows a router to maintain its current BGP configuration while it advertises a different AS number to new connections? A. local-AS B. next-hop-self C. allow-AS in D. soft reset

Answer : A Explanation: The local-AS feature allows a router to appear to be a member of a second autonomous system (AS), in addition to its real AS. This feature can only be used for true eBGP peers. The local-AS feature is useful if ISP-A purchases ISP-B, but ISP-B's customers do not want to modify any peering arrangements or configurations. The local-AS feature allows routers in ISP-B to become members of ISP-A's AS. At the same time, these routers appear to their customers to retain their ISP-B AS number. Reference: http://www.cisco.com/c/en/us/support/docs/ip/border-gateway-protocol- bgp/13761-39.html

Question No : 141 - Topic 3 Which action does route poisoning take that serves as a loop-prevention method? A. It immediately sends routing updates with an unreachable metric to all devices. B. It immediately sends routing updates with a metric of 255 to all devices. C. It prohibits a router from advertising back onto the interface from which it was learned. D. It advertises a route with an unreachable metric back onto the interface from which it was learned. E. It poisons the route by tagging it uniquely within the network.

Answer : A Explanation: With route poisoning, when a router detects that one of its connected routes has failed, the router will poison the route by assigning an infinite metric to it and advertising it to neighbors.

Question No : 261 - Topic 3 Which group of neighbors can be configured as a BGP peer group? A. a group of iBGP neighbors that have the same outbound route policies B. a group of iBGP and eBGP neighbors that have the same inbound distribute-list C. a group of eBGP neighbors in the same autonomous system that have different outbound route policies D. a group of iBGP neighbors that have different outbound route policies

Answer : A Explanation: You can group BGP neighbors who share the same outbound policies together in what is called a BGP peer group. Instead of configuring each neighbor with the same policy individually, a peer group allows you to group the policies which can be applied to individual peers thus making efficient update calculation along with simplified configuration. Reference: http://www.cisco.com/c/en/us/support/docs/ip/border-gateway-protocol- bgp/13755-29.html

Question No : 308 - Topic 3 What is the preferred method to improve neighbor loss detection in EIGRP? A. EIGRP natively detects neighbor down immediately, and no additional feature or configuration is required. B. BFD should be used on interfaces that support it for rapid neighbor loss detection. C. Fast hellos (subsecond) are preferred for EIGRP, so that it learns rapidly through its own mechanisms. D. Fast hellos (one-second hellos) are preferred for EIGRP, so that it learns rapidly through its own mechanisms.

Answer : B Explanation: Bi-directional Forwarding Detection (BFD) provides rapid failure detection times between forwarding engines, while maintaining low overhead. It also provides a single, standardized method of link/device/protocol failure detection at any protocol layer and over any media. Reference: Bidirectional Forwarding Detection for EIGRP http://www.cisco.com/en/US/technologies/tk648/tk365/tk207/technologies_white_paper090 0aecd80243fe7.html

Question No : 215 - Topic 3 You are tasked with configuring a router on an OSPF domain to import routes from an EIGRP domain and summarize the routes to 192.168.64.0. Which statement configures the summarized route and provides equal-path route redundancy? A. area 32 range 192.168.64.0 255.255.192.0 cost 100 B. area 32 range 192.168.64.0 255.255.63.0 cost 100 C. area 32 range 192.168.64.0 255.255.64.0 cost 100 D. area 32 range 192.168.64.0 255.255.192.0 multi-path

Answer : A Explanation: area range To consolidate and summarize routes at an area boundary, use the area range command in router configuration mode. To disable this function, use the no form of this command. Syntax Description area-id Identifier of the area about which routes are to be summarized. It can be specified as either a decimal value or as an IP address. ip-address IP address. mask IP address mask. advertise (Optional) Sets the address range status to advertise and generates a Type 3 summary link-state advertisement (LSA). not-advertise (Optional) Sets the address range status to DoNotAdvertise. The Type 3 summary LSA is suppressed, and the component networks remain hidden from other networks. cost cost (Optional) Metric or cost for this summary route, which is used during OSPF SPF calculation to determine the shortest paths to the destination. The value can be 0 to 16777215. Reference: http://www.cisco.com/c/en/us/td/docs/ios/12_2/iproute/command/reference/fiprrp_r/1rfospf. html#wp1017596

Question No : 294 - Topic 3 When EIGRP is used as the IPv4 PE-CE protocol, which two requirements must be configured before the BGP IPv4 address family can be configured? (Choose two.) A. the route distinguisher B. the virtual routing and forwarding instance C. the loopback interface D. the router ID

Answer : A,B Explanation: A VRF must be created, and a route distinguisher and route target must be configured in order for the PE routers in the BGP network to carry EIGRP routes to the EIGRP CE site. The VRF must also be associated with an interface in order for the PE router to send routing updates to the CE router. Prerequisites Before this feature can be configured, MPLS and CEF must be configured in the BGP network, and multiprotocol BGP and EIGRP must be configured on all PE routers that provide VPN services to CE routers. Reference: http://www.cisco.com/c/en/us/td/docs/ios/12_0s/feature/guide/seipecec.html#wp1083316

Question No : 234 - Topic 3 Which two options are valid for the number of bytes in a BGP AS number? (Choose two.) A. 2 bytes B. 4 bytes C. 6 bytes D. 8 bytes E. 16 bytes

Answer : A,B Explanation: During the early time of BGP development and standardization, it was assumed that availability of a 16 bit binary number to identify the Autonomous System (AS) within BGP would have been more than sufficient. The 16 bit AS number, also known as the 2-byte AS number, provides a pool of 65536 unique Autonomous System numbers. The IANA manages the available BGP Autonomous System Numbers (ASN) pool, with the assignments being carried out by the Regional Registries. The current consumption rate of the publicly available AS numbers suggests that the entire public 2-byte ASN pool will be fully depleted. A solution to this depletion is the expansion of the existing 2-byte AS number to a 4-byte AS number, which provides a theoretical 4,294,967,296 unique AS numbers. ARIN has made the following policy changes in conjunction with the adoption of the solution. The Cisco IOS BGP "4-byte ASN" feature allows BGP to carry a Autonomous System Number (ASN) encoded as a 4-byte entity. The addition of this feature allows an operator to use an expanded 4-byte AS number granted by IANA.

Question No : 283 - Topic 3 Which two options are benefits of EIGRP OTP? (Choose two.) A. It allows EIGRP routers to peer across a service provider without the service provider involvement. B. It allows the customer EIGRP domain to remain contiguous. C. It requires only minimal support from the service provider. D. It allows EIGRP neighbors to be discovered dynamically. E. It fully supports multicast traffic. F. It allows the administrator to use different autonomous system numbers per EIGRP domain.

Answer : A,B Explanation: EIGRP Over the Top (OTP) allows EIGRP routers to peer across a service provider infrastructure without the SPs involvement. In fact with OTP, the provider wont see customer routes at all. EIGRP OTP acts as a provider-independent overlay that transports customer data between the customers routers. To the customer, the EIGRP domain is contiguous. A customers EIGRP router sits at the edge of the provider cloud, and peers with another EIGRP router a different location across the cloud. Learned routes feature a next hop of the customer router not the provider. Good news for service providers is that customers can deploy EIGRP OTP with their involvement Reference: http://ethancbanks.com/2013/08/01/an-overview-of-eigrp-over-the-top-otp/

Question No : 139 - Topic 3 Packets from a router with policy-based routing configured are failing to reach the next hop. Which two additions can you make to the router configuration to enable the packets to flow correctly? (Choose two.) A. Enable ip proxy-arp on the exiting interface. B. Specify the next hop as an address. C. Specify the next hop as an interface. D. Add a match-any permit statement to the route map.

Answer : A,B Explanation: Here is an example: Router(config)#route-map Engineers permit 20 Router(config-route-map)#match ip address 2 Router(config-route-map)#set interface Ethernet1 Here, instead of specifying a next-hop, it specifies that any packets matching this rule will be forwarded directly out the interface Ethernet1. This means that either the destination device must be on this segment, or there must be a router configured with Proxy ARP that can forward the packet to the ultimate destination.

Question No : 196 - Topic 3 Which two options describe two functions of a neighbor solicitation message? (Choose two.) A. It requests the link-layer address of the target. B. It provides its own link-layer address to the target. C. It requests the site-local address of the target. D. It provides its own site-local address to the target. E. It requests the admin-local address of the target. F. It provides its own admin-local address to the target.

Answer : A,B Explanation: Neighbor solicitation messages are sent on the local link when a node wants to determine the link-layer address of another node on the same local link (see the figure below). When a node wants to determine the link-layer address of another node, the source address in a neighbor solicitation message is the IPv6 address of the node sending the neighbor solicitation message. The destination address in the neighbor solicitation message is the solicited-node multicast address that corresponds to the IPv6 address of the destination node. The neighbor solicitation message also includes the link-layer address of the source node. Figure 1. IPv6 Neighbor Discovery: Neighbor Solicitation Message After receiving the neighbor solicitation message, the destination node replies by sending a neighbor advertisement message, which has a value of 136 in the Type field of the ICMP packet header, on the local link. The source address in the neighbor advertisement message is the IPv6 address of the node (more specifically, the IPv6 address of the node interface) sending the neighbor advertisement message. The destination address in the neighbor advertisement message is the IPv6 address of the node that sent the neighbor solicitation message. The data portion of the neighbor advertisement message includes the link-layer address of the node sending the neighbor advertisement message. After the source node receives the neighbor advertisement, the source node and destination node can communicate. Reference: http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/ipv6_basic/configuration/xe- 3s/ip6b-xe-3s-book/ip6-neighb-disc-xe.html

Question No : 193 - Topic 3 Which two statements about the ipv6 ospf authentication command are true? (Choose two.) A. The command is required if you implement the IPsec AH header. B. The command configures an SPI. C. The command is required if you implement the IPsec TLV. D. The command can be used in conjunction with the SPI authentication algorithm. E. The command must be configured under the OSPFv3 process. question_answerVIEW ANSWER SHOW COMMENTS 0

Answer : A,B Explanation: OSPFv3 requires the use of IPsec to enable authentication. Crypto images are required to use authentication, because only crypto images include the IPsec API needed for use with OSPFv3. In OSPFv3, authentication fields have been removed from OSPFv3 packet headers. When OSPFv3 runs on IPv6, OSPFv3 requires the IPv6 authentication header (AH) or IPv6 ESP header to ensure integrity, authentication, and confidentiality of routing exchanges. IPv6 AH and ESP extension headers can be used to provide authentication and confidentiality to OSPFv3. To use the IPsec AH, you must enable the ipv6 ospf authentication command. To use the IPsec ESP header, you must enable the ipv6 ospf encryption command. The ESP header may be applied alone or in combination with the AH, and when ESP is used, both encryption and authentication are provided. Security services can be provided between a pair of communicating hosts, between a pair of communicating security gateways, or between a security gateway and a host. To configure IPsec, you configure a security policy, which is a combination of the security policy index (SPI) and the key (the key is used to create and validate the hash value). IPsec for OSPFv3 can be configured on an interface or on an OSPFv3 area. For higher security, you should configure a different policy on each interface configured with IPsec. If you configure IPsec for an OSPFv3 area, the policy is applied to all of the interfaces in that area, except for the interfaces that have IPsec configured directly. Once IPsec is configured for OSPFv3, IPsec is invisible to you. Reference: http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_ospf/configuration/15- sy/iro-15-sy-book/ip6-route-ospfv3-auth-ipsec.html

Question No : 203 - Topic 3 Which two options are EIGRP route authentication encryption modes? (Choose two.) A. MD5 B. HMAC-SHA-256bit C. ESP-AES D. HMAC-AES

Answer : A,B Explanation: Packets exchanged between neighbors must be authenticated to ensure that a device accepts packets only from devices that have the same preshared authentication key. Enhanced Interior Gateway Routing Protocol (EIGRP) authentication is configurable on a per-interface basis; this means that packets exchanged between neighbors connected through an interface are authenticated. EIGRP supports message digest algorithm 5 (MD5) authentication to prevent the introduction of unauthorized information from unapproved sources. MD5 authentication is defined in RFC 1321. EIGRP also supports the Hashed Message Authentication Code-Secure Hash Algorithm-256 (HMAC-SHA-256) authentication method. Reference: http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_eigrp/configuration/xe- 3s/ire-xe-3s-book/ire-sha-256.html

Question No : 314 - Topic 3 What are two advantages to using Asynchronous mode instead of Demand mode for BFD? (Choose two.) A. Asynchronous mode requires half as many packets as Demand mode for failure detection. B. Asynchronous mode can be used in place of the echo function. C. Asynchronous mode supports a larger number of BFD sessions. D. Asynchronous mode requires one fourth as many packets as Demand mode for failure detection. E. Asynchronous mode's round-trip jitter is less than that of Demand mode.

Answer : A,B Explanation: Pure Asynchronous mode is advantageous in that it requires half as many packets to achieve a particular Detection Time as does the Echo function. It is also used when the Echo function cannot be supported for some reason. Reference: https://tools.ietf.org/html/rfc5880

Question No : 246 - Topic 3 Which two statements about SoO checking in EIGRP OTP deployments are true? (Choose two). A. During the import process, the SoO value in BGP is checked against the SoO value of the site map. B. During the reception of an EIGRP update, the SoO value in the EIGRP update is checked against the SoO value of the site map on the ingress interface. C. At the ingress of the PE/CE link, the SoO in the EIGRP update is checked against the SoO within the PE/CE routing protocol. D. At the egress of the PE/CE link, the SoO is checked against the SoO within the PE/CE routing protocol. E. The SoO is checked at the ingress of the backdoor link. F. The SoO is checked at the egress of the backdoor link.

Answer : A,B Explanation: SoO checking: During the import process the SoO value in BGP update is checked against the SoO value of the site-map attached to VRF interface. The update is propagated to CE only if there is no match (this check is done regardless of protocol used on PE/CE link). At reception of EIGRP update, the SoO value in the EIGRP update is checked against the SoO value of site-map attached to the incoming interface. This update is accepted only if there is no match (this check can optionally be done on backdoor router). Reference: http://www.cisco.com/c/en/us/products/collateral/ios-nx-os-software/ip- routing/whitepaper_C11-730404.html

Question No : 156 - Topic 3 Which two features improve BGP convergence? (Choose two.) A. next-hop address tracking B. additional paths C. advertise map D. communities E. soft reconfiguration

Answer : A,B Explanation: The BGP Support for Next-Hop Address Tracking feature is enabled by default when a supporting Cisco software image is installed. BGP next-hop address tracking is event driven. BGP prefixes are automatically tracked as peering sessions are established. Next- hop changes are rapidly reported to the BGP routing process as they are updated in the RIB. This optimization improves overall BGP convergence by reducing the response time to next-hop changes for routes installed in the RIB. When a best path calculation is run in between BGP scanner cycles, only next-hop changes are tracked and processed. BGP routers and route reflectors (RRs) propagate only their best path over their sessions. The advertisement of a prefix replaces the previous announcement of that prefix (this behavior is known as an implicit withdraw). The implicit withdraw can achieve better scaling, but at the cost of path diversity. Path hiding can prevent efficient use of BGP multipath, prevent hitless planned maintenance, and can lead to MED oscillations and suboptimal hot-potato routing. Upon nexthop failures, path hiding also inhibits fast and local recovery because the network has to wait for BGP control plane convergence to restore traffic. The BGP Additional Paths feature provides a generic way of offering path diversity; the Best External or Best Internal features offer path diversity only in limited scenarios. The BGP Additional Paths feature provides a way for multiple paths for the same prefix to be advertised without the new paths implicitly replacing the previous paths. Thus, path diversity is achieved instead of path hiding. References: http://www.cisco.com/en/US/docs/ios-xml/ios/iproute_bgp/configuration/15- 1sg/irg-nexthop-track.html http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_bgp/configuration/xe-3s/irg-xe-3s- book/bgp_additional_paths.html

Question No : 192 - Topic 3 Which two options are mandatory components of a multiprotocol BGP VPN-IPv4 address? (Choose two.) A. a route distinguisher B. an IPv4 address C. a route target D. an MPLS label E. a system ID F. an area ID

Answer : A,B Explanation: The IP prefix is a member of the IPv4 address family. After the PE device learns the IP prefix, the PE converts it into a VPN-IPv4 prefix by combining it with an 8-byte route distinguisher (RD). The generated prefix is a member of the VPN-IPv4 address family. It uniquely identifies the customer address, even if the customer site is using globally nonunique (unregistered private) IP addresses. The route distinguisher used to generate the VPN-IPv4 prefix is specified by a configuration command associated with the virtual routing and forwarding (VRF) instance on the PE device. Reference: http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/mp_l3_vpns/configuration/15- mt/mp-l3-vpns-15-mt-book/mp-bgp-mpls-vpn.html

Question No : 280 - Topic 3 Which two loop-prevention mechanisms are implemented in BGP? (Choose two.) A. A route with its own AS in the AS_PATH is dropped automatically if the route reenters its own AS. B. A route with its own cluster ID in the CLUSTER_LIST is dropped automatically when the route reenters its own AS. C. The command bgp allowas-in enables a route with its own AS_PATH to be dropped when it reenters its own AS. D. The command bgp bestpath as-path ignore enables the strict checking of AS_PATH so that they drop routes with their own AS in the AS_PATH. E. The command bgp bestpath med missing-as-worst assigns the smallest possible MED, which directly prevents a loop.

Answer : A,B Explanation: When dealing with the possibility of routing updates making their way back into an AS, BGP relies on the information in the AS_path for loop detection. An update that tries to make its way back into the AS it was originated from will be dropped by the border router. With the introduction of route reflectors, there is a potential for having routing loops within an AS. A routing update that leaves a cluster might find its way back inside the cluster. Loops inside the AS cannot be detected by the traditional AS_path approach because the routing updates have not left the AS yet. BGP offers two extra measures for loop avoidance inside an AS when route reflectors are configured. Using an Originator ID ID is a 4-byte, optional, nontransitive BGP attribute (type code 9) that is created by the route reflector. This attribute carries the router ID of the originator of the route in the local AS. If, because of poor configuration, the update comes back to the originator, the originator ignores it. Using a Cluster List is an optional, nontransitive BGP attribute (type code 10). Each cluster is represented with a cluster ID. A cluster list is a sequence of cluster IDs that an update has traversed. When a route reflector sends a route from its clients to nonclients outside the cluster, it appends the local cluster ID to the cluster list. If the route reflector receives an update whose cluster list contains the local cluster ID, the update is ignored. This is basically the same concept as the AS_path list applied between the clusters inside the AS. Reference: http://borg.uu3.net/cisco/inter_arch/page11.html

Question No : 287 - Topic 3 Which two statements about IS-IS are true? (Choose two.) A. The default hello interval is 10 seconds and the default hold timer is 30 seconds. B. The hello interval can be changed on a per-interface basis with the command isis hello- multiplier. C. Both routers need to have the same hello intervals and hold timers in order to form IS-IS neighbors. D. Both IS-IS routers need to have the same capabilities in the hello packet in order to form neighbors.

Answer : A,B Explanation: isis hello-interval To specify the length of time between hello packets that the Cisco IOS software sends, use the isis hello-interval command in interface configuration mode. By default, a value three times the hello interval seconds is advertised as the hold time in the hello packets sent. (Change the multiplier of 3 by specifying the isis hello-multiplier command.) With smaller hello intervals, topological changes are detected faster, but there is more routing traffic. The default is 10 seconds. Reference: http://www.cisco.com/c/en/us/td/docs/ios/12_2/iproute/command/reference/fiprrp_r/1rfisis.ht ml

Question No : 202 - Topic 3 Which two OSPF LSA types are flooded within the originating area? (Choose two.) A. type 1, Router LSA B. type 2, Network LSA C. type 3, Network Summary LSA D. type 4, ASBR Summary LSA E. type 6, Group Membership LSA F. type 9, Opaque LSA

Answer : A,B Explanation: to communicate link state information between neighbors. A brief review of the most applicable LSA types: ✑ Type 1 - Represents a router ✑ Type 2 - Represents the pseudonode (designated router) for a multiaccess link ✑ Type 3 - A network link summary (internal route) ✑ Type 4 - Represents an ASBR ✑ Type 5 - A route external to the OSPF domain ✑ Type 7 - Used in stub areas in place of a type 5 LSA LSA types 1 and 2 are found in all areas, and are never flooded outside of an area. They are only flooded within the area that they originated from. Reference: http://packetlife.net/blog/2008/jun/24/ospf-area-types/

Question No : 291 - Topic 3 Which three statements about IS-IS are true? (Choose three.) A. IS-IS is not encapsulated in IP. B. IS-IS is directly encapsulated in the data link layer. C. 0XFEFE is used in the Layer 2 header to identify the Layer 3 protocol. D. IS-IS uses protocol ID 93. E. IS-IS can be used to route the IPX protocol. F. IS-IS is an IETF standard.

Answer : A,B,C Explanation: IS-IS is an Interior Gateway Protocol (IGP) for routing OSI. IS-IS packets are not encapsulated in CLNS or IP but are encapsulated directly in the data-link layer. The IS-IS protocol family is OSI, and values such as 0xFE and 0xFEFE are used by the data-link protocol to identify the Layer 3 protocol as OSI. Reference: http://www.cisco.com/en/US/products/ps6599/products_white_paper09186a00800a3e6f.sh tml

Question No : 144 - Topic 3 Which three options are three of the default EIGRP administrative distances? (Choose three.) A. Internal, 90 B. External, 170 C. Summary, 5 D. Outside Local, 100 E. Inside Local, 180 F. Inside Global, 1

Answer : A,B,C Explanation: The following table lists the default administrative distances for various routing protocols used on Cisco routers. Routing Protocol Administrative distance Directly connected interface Static route out an interface Static route to next-hop address DMNR - Dynamic Mobile Network Routing EIGRP summary route External BGP Internal EIGRP IGRP OSPF IS-IS Routing Information Protocol (RIP) Exterior Gateway Protocol (EGP) On Demand Routing (ODR) External EIGRP Internal BGP Floating Static Route (ex. DHCP-learned) Unknown Reference: http://en.wikipedia.org/wiki/Administrative_distance

Question No : 195 - Topic 3 Which three statements about RIP timers are true? (Choose three.) A. The default update timer is 30 seconds. B. The default invalid timer is 180 seconds. C. The default holddown timer is 180 seconds. D. The default flush timer is 60 seconds. E. The default scan timer is 60 seconds. F. The default hello timer is 5 seconds. question_answerVIEW ANSWER SHOW COMMENTS

Answer : A,B,C Explanation: The routing information protocol uses the following timers as part of its operation: ✑ Update Timer ✑ Invalid Timer ✑ Flush Timer ✑ Holddown Timer Update Timer The update timer controls the interval between two gratuitous Response Message. By default the value is 30 seconds. The response message is broadcast to all its RIP enabled interface. Invalid Timer The invalid timer specifies how long a routing entry can be in the routing table without being updated. This is also called as expiration Timer. By default, the value is 180 seconds. After the timer expires the hop count of the routing entry will be set to 16, marking the destination as unreachable. Flush Timer The flush timer controls the time between the route is invalidated or marked as unreachable and removal of entry from the routing table. By default the value is 240 seconds. This is 60 seconds longer than Invalid timer. So for 60 seconds the router will be advertising about this unreachable route to all its neighbors. This timer must be set to a Hold-down Timer The hold-down timer is started per route entry, when the hop count is changing from lower value to higher value. This allows the route to get stabilized. During this time no update can be done to that routing entry. This is not part of the RFC 1058. This is Cisco's implementation. The default value of this timer is 180 seconds. Reference: http://en.wikipedia.org/wiki/Routing_Information_Protocol#Timers

Question No : 220 - Topic 3 Which three statements about EIGRP and BFD are true? (Choose three.) A. BFD is independent of the routing protocol, so it can be used as a generic failure detection mechanism for EIGRP. B. Some parts of BFD can be distributed to the data plane, so it can be less CPU-intensive than reduced timers, which exist wholly at the control plane. C. Reduced EIGRP timers have an absolute minimum detection timer of 1-2 seconds; BFD can provide sub-second failure detection. D. BFD is tied to specific routing protocols and can be used for generic fault detection for the OSPF, EIGRP, and BGP routing protocols. E. BFD is dependent on the EIGRP routing protocol, so it can be used as a specific failure detection mechanism. F. BFD resides on the control plane, so it is less CPU-intensive than if it resided on the data plane.

Answer : A,B,C Explanation: There are several advantages to implementing BFD over reduced timer mechanisms for routing protocols: Although reducing the EIGRP, IS-IS, and OSPF timers can result in minimum detection timer of one to two seconds, BFD can provide failure detection in less than one second. Because BFD is not tied to any particular routing protocol, it can be used as a generic and consistent failure detection mechanism for EIGRP, IS-IS, and OSPF. Because some parts of BFD can be distributed to the data plane, it can be less CPU- intensive than the reduced EIGRP, IS-IS, and OSPF timers, which exist wholly at the control plane. Reference: http://www.cisco.com/c/en/us/td/docs/ios/12_0s/feature/guide/fs_bfd.html

Question No : 157 - Topic 3 Which three routing protocols utilize TLVs? (Choose three.) A. BGP B. IS-IS C. ODR D. OSPF E. EIGRP F. RIP

Answer : A,B,E Explanation: IS-IS, originally designed for Open System Interconnection (OSI) routing, uses TLV parameters to carry information in Link State Packets (LSPs). The TLVs make IS-IS extendable. IS-IS can therefore carry different kinds of information in the LSPs. Several routing protocols use TLVs to carry a variety of attributes. Cisco Discovery Protocol (CDP), Label Discovery Protocol (LDP), and Border Gateway Protocol (BGP) are examples of protocols that use TLVs. BGP uses TLVs to carry attributes such as Network Layer Reachability Information (NLRI), Multiple Exit Discriminator (MED), and local pReference: The IP header of the EIGRP packet specifies IP protocol number 88 within it, and the maximum length of the packet will be the IP MTU of the interface on which it is transmitted, most of the time 1500 octets. Following the IP header is the various Type/Length/Value (TLV) triplets. These TLVs will not only carry the route entries but also provide fields for the management of the DUAL process, multicast sequencing, and IOS software versions from the router. References: http://www.cisco.com/c/en/us/support/docs/ip/integrated-intermediate-system- to-intermediate-system-is-is/5739-tlvs-5739.html http://ericleahy.com/index.php/eigrp-packets-neighborships/

Question No : 317 - Topic 3 Which two functions are performed by the DR in OSPF? (Choose two.) A. The DR originates the network LSA on behalf of the network. B. The DR is responsible for the flooding throughout one OSPF area. C. The DR forms adjacencies with all other OSPF routers on the network, in order to synchronize the LSDB across the adjacencies. D. The DR is responsible for originating the type 4 LSAs into one area.

Answer : A,C Explanation: The DR originates the network LSA (LSA Type 2) which lists all the routers on the segment it is adjacent to -> A is correct. Types 2 are ooded within its area only; does not cross ABR -> B is incorrect. The broadcast and non-broadcast network types elect a DR/BDR. They form adjacencies to all other OSPF routers on the network and help synchronize the Link State Database (LSDB) across the adjacencies -> C is correct. LSAs Type 4 are originated by the ABR to describe an ASBR to routers in other areas so that routers in other areas know how to get to external routes through that ASBR -> D is incorrect.

Question No : 165 - Topic 3 Which three statements about the route preference of IS-IS are true? (Choose three.) A. An L1 path is preferred over an L2 path. B. An L2 path is preferred over an L1 path. C. Within each level, a path that supports optional metrics is preferred over a path that supports only the default metric. D. Within each level of metric support, the path with the lowest metric is preferred. E. The Cisco IS-IS implementation usually performs equal cost path load balancing on up to eight paths. F. Both L1 and L2 routes will be installed in the routing table at the same time.

Answer : A,C,D Explanation: Given multiple possible routes to a particular destination, an L1 path is preferred over an L2 path. Within each level, a path that supports the optional metrics is preferred over a path that supports only the default metric. (Again, Cisco supports only the default metric, so the second order of preference is not relevant to Cisco routers.) Within each level of metric support, the path with the lowest metric is preferred. If multiple equal-cost, equal-level paths are found by the Decision process, they are all entered into the route table. The Cisco IS-IS implementation usually performs equal-cost load balancing on up to six paths. Reference: http://www.realccielab.org/operation-of-integrated-is-is.html

Question No : 149 - Topic 3 Which three values can be used to tag external EIGRP routes? (Choose three.) A. The router ID of the router that redistributed the route B. The administrative distance of the external protocol C. The protocol ID of the external protocol D. The cost to reach the router that redistributed the route E. The metric from the external protocol F. The router ID of the router from which the external protocol route was learned

Answer : A,C,E Explanation: EIGRP has the notion of internal and external routes. Internal routes are ones that have been originated within an EIGRP autonomous system (AS). Therefore, a directly attached network that is configured to run EIGRP is considered an internal route and is propagated with this information throughout the EIGRP AS. External routes are ones that have been learned by another routing protocol or reside in the routing table as static routes. These routes are tagged individually with the identity of their origination. External routes are tagged with the following information: ✑ The router ID of the EIGRP router that redistributed the route. ✑ The AS number where the destination resides. ✑ A configurable administrator tag. ✑ Protocol ID of the external protocol. ✑ The metric from the external protocol. ✑ Bit flags for default routing. Reference: http://www.cisco.com/c/en/us/support/docs/ip/enhanced-interior-gateway- routing-protocol-eigrp/13669-1.html#route_tagging

Question No : 136 - Topic 3 Which option is the default number of routes over which EIGRP can load balance? A. 1 B. 4 C. 8 D. 16

Answer : B Explanation: By default, EIGRP load-shares over four equal-cost paths. For load sharing to happen, the routes to load-share over must show up in the IP forwarding table or with the show ip route command. Only when a route shows up in the forwarding table with multiple paths to it will load sharing occur. Reference: http://www.informit.com/library/content.aspx?b=CCIE_Practical_Studies_I&seqNum=126

Question No : 268 - Topic 3 What are two reasons to define static peers in EIGRP? (Choose two.) A. Security requirements do not allow dynamic learning of neighbors. B. The link between peers requires multicast packets. C. Back-level peers require static definition for successful connection. D. The link between peers requires unicast packets.

Answer : A,D Explanation: There are two ways we can create EIGRP neighbor relationship: + Use network command. This is the more popular way to create EIGRP neighbor relationship. That router will check which interfaces whose IP addresses belong to the and turn EIGRP on that interface. EIGRP messages are sent via multicast packets. + Use neighbor commanD. The interface(s) that have this command applied no longer send or receive EIGRP multicast packets. EIGRP messages are sent via unicast. The router only accepts EIGRP packets from peers that are explicitly configured with a neighbor statement. Consequently, any messages coming from routers without a corresponding neighbor statement are discarded. This helps prevent the insertion of unauthorized routing peers -> A and D are correct.

Question No : 302 - Topic 3 Which two statements about the metric-style wide statement as it applies to route redistribution are true? (Choose two.) A. It is used in IS-IS. B. It is used in OSPF. C. It is used in EIGRP. D. It is used for accepting TLV. E. It is used in PIM for accepting mroutes. F. It is used for accepting external routes.

Answer : A,D Explanation: To configure a router running IS-IS to generate and accept only new-style TLVs (TLV stands for type, length, and value object), use the metric-style wide command. Reference: http://www.cisco.com/c/en/us/td/docs/ios/12_0s/feature/guide/TE_1208S.html#wp49409

Question No : 257 - Topic 3 Which term describes an EIGRP route that has feasible successors? A. active B. passive C. redistributed D. invalid

Answer : B Explanation: A topology table entry for a destination can have one of two states. A route is considered in the Passive state when a router is not performing a route recomputation. The route is in Active state when a router is undergoing a route recomputation. If there are always feasible successors, a route never has to go into Active state and avoids a route recomputation. When there are no feasible successors, a route goes into Active state and a route recomputation occurs. A route recomputation commences with a router sending a query packet to all neighbors. Neighboring routers can either reply if they have feasible successors for the destination or optionally return a query indicating that they are performing a route recomputation. While in Active state, a router cannot change the next- hop neighbor it is using to forward packets. Once all replies are received for a given query, the destination can transition to Passive state and a new successor can be selected. Reference: http://docwiki.cisco.com/wiki/Enhanced_Interior_Gateway_Routing_Protocol

Question No : 304 - Topic 3 Which statement about the feasible distance in EIGRP is true? A. It is the maximum metric that should feasibly be considered for installation in the RIB. B. It is the minimum metric to reach the destination as stored in the topology table. C. It is the metric that is supplied by the best next hop toward the destination. D. It is the maximum metric possible based on the maximum hop count that is allowed.

Answer : B Explanation: An EIGRP router advertises each destination it can reach as a route with an attached metric. This metric is called the route's reported distance (the term advertised distance has also been used in older documentation). A successor route for any given destination is chosen as having the lowest computed feasible distance; that is, the lowest sum of reported distance plus the cost to get to the advertising router. By default, an EIGRP router will store only the route with the best (lowest) feasible distance in the routing table (or, multiple routes with equivalent feasible distances). Reference: http://packetlife.net/blog/2010/aug/9/eigrp-feasible-successor-routes/

Question No : 206 - Topic 3 Which statement about the BGP originator ID is true? A. The route reflector always sets the originator ID to its own router ID. B. The route reflector sets the originator ID to the router ID of the route reflector client that injects the route into the AS. C. The route reflector client that injects the route into the AS sets the originator ID to its own router ID. D. The originator ID is set to match the cluster ID.

Answer : B Explanation: An RR reflecting the route received from a RR-Client adds: ✑ Originator ID- a 4-byte BGP attribute that is created by the RR. This attribute carries the Router ID of the originator of the route in the local AS. If the update comes back to the originator, it ignores the update. ✑ Cluster List- A Cluster List is a list of Cluster IDs that an update has traversed. When a route reflector sends a route received from a client to a non-client, it appends the local Cluster ID. If a route reflector receives a route whose Cluster List contains the local Cluster ID, it ignores the update. Reference: https://sites.google.com/site/amitsciscozone/home/bgp/bgp-route-reflectors

Question No : 189 - Topic 3 Which timer expiration can lead to an EIGRP route becoming stuck in active? A. hello B. active C. query D. hold

Answer : B Explanation: As noted above, when a route goes into the active state, the router queries its neighbors to find a path to the pertinent network. At this point, the router starts a three minute active timer by which time it must receive replies from all queried neighbors. If a neighbor has feasible successors for the route, it will recalculate its own local distance to the network and report this back. However, if a neighbor does not have a feasible successor, it also goes into active state. In some cases, multiple routers along multiple query paths will go into active state as routers continue to query for the desired route. In most cases, this process will yield responses from all queried routers and the sought after route will transition back into the passive state within the three minute SIA query timer. In the case that none of the queried routers can provide a feasible successor, the route is cleared. In some cases, a response is not received between two neighbor routers because of link failures, congestion or some other adverse condition in either the network or on the queried router, and the three minute active timer expires on the router originating the query. When this happens, the querying router that did not receive a response logs a DUAL-3-SIA or stuck-in-active error for the route and then drops and restarts its adjacency with the non- responding router Reference: http://www.packetdesign.com/resources/technical-briefs/diagnosing-eigrp- stuck-active

Question No : 161 - Topic 3 Which BGP feature allows BGP routing tables to be refreshed without impacting established BGP sessions? A. BGP synchronization B. soft reconfiguration C. confederations D. hard reset question_answerVIEW ANSWER

Answer : B Explanation: Clearing a BGP session using a hard reset invalidates the cache and results in a negative impact on the operation of networks as the information in the cache becomes unavailable. Soft reset is recommended because it allows routing tables to be reconfigured and activated without clearing the BGP session. Soft reset is done on a per-neighbor basis. Reference: http://www.cisco.com/en/US/products/ps6599/products_data_sheet09186a0080087b3a.ht ml

Question No : 184 - Topic 3 Which bit should be set in the link-state PDU of an IS-IS L1/L2 router to indicate that it is a potential exit point of the area? A. the ABR bit B. the ATT bit C. the down bit D. the P bit

Answer : B Explanation: Default routing is achieved in two distinct ways with Integrated IS-IS: Set by a Level 1/Level 2 router in its own Level 1 LSP and used to indicate to all Level 1 routers (within the area) that this router is a potential exit point of the area. Level 1-only routers will default to the nearest attached Level 2 router. Can be configured in Level 1 as well as Level 2. The default route (0.0.0.0/0) is inserted in the router LSP (Level 1 or Level 2, according to the configuration command) and the LSP is flooded according to the router type (Level 1 or Level 2). A Level 2 router doesn't need to have a default route to originate a default route. Reference: http://www.cisco.com/en/US/products/ps6599/products_white_paper09186a00800a3e6f.sh tml

Question No : 197 - Topic 3 With which ISs will an IS-IS Level 1 IS exchange routing information? A. Level 1 ISs B. Level 1 ISs in the same area C. Level 1 and Level 2 ISs D. Level 2 ISs

Answer : B Explanation: IS-IS differs from OSPF in the way that "areas" are defined and routed between. IS-IS routers are designated as being: Level 1 (intra-area); Level 2 (inter area); or Level 1-2 (both). Level 2 routers are inter area routers that can only form relationships with other Level 2 routers. Routing information is exchanged between Level 1 routers and other Level 1 routers, and Level 2 routers only exchange information with other Level 2 routers. Level 1-2 routers exchange information with both levels and are used to connect the inter area routers with the intra area routers. Reference: http://en.wikipedia.org/wiki/IS-IS

Question No : 188 - Topic 3 If two OSPF type 3 prefixes have the same metric, and are within the same process, which prefix(es) are installed into the routing table? A. The route whose originator has the lower router ID. B. Both routes are installed. C. The route whose originator has the higher router ID. D. The first route that is learned.

Answer : B Explanation: OSPF allows multiple equal-cost paths to the same destination. Since all link-state information is flooded and used in the SPF calculation, multiple equal cost paths can be computed and used for routing, and each route will be installed in the routing table.

Question No : 315 - Topic 3 Which statement about the OSPF Loop-Free Alternate feature is true? A. It is supported on routers that are configured with virtual links. B. It is supported in VRF OSPF instances. C. It is supported when a traffic engineering tunnel interface is protected. D. It is supported when traffic can be redirected to a primary neighbor.

Answer : B Explanation: Restrictions for OSPF IPv4 Remote Loop-Free Alternate IP Fast Reroute ✑ The OSPF IPv4 Remote Loop-Free Alternate IP Fast Reroute feature is not supported on devices that are virtual links headends. ✑ The feature is supported only in global VPN routing and forwarding (VRF) OSPF instances. ✑ The only supported tunneling method is MPLS. ✑ You cannot configure a traffic engineering (TE) tunnel interface as a protected interface. Use the MPLS Traffic EngineeringFast Reroute Link and Node Protection feature to protect these tunnels. For more information, see the MPLS Traffic EngineeringFast Reroute Link and Node Protection section in the Multiprotocol Label Switching Configuration Guide. ✑ You can configure a TE tunnel interface in a repair path, but OSPF will not verify the tunnels placement; you must ensure that it is not crossing the physical interface that it is intended to protect. ✑ Not all routes can have repair paths. Multipath primary routes might have repair paths for all, some, or no primary paths, depending on the network topology, the connectivity of the computing router, and the attributes required of repair paths. ✑ Devices that can be selected as tunnel termination points must have a /32 address advertised in the area in which remote LFA is enabled. This address will be used as a tunnel termination IP. If the device does not advertise a /32 address, it may not be used for remote LFA tunnel termination. ✑ All devices in the network that can be selected as tunnel termination points must be configured to accept targeted LDP sessions using the mpls ldp discovery targeted-hello accept command. Reference: http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_ospf/configuration/xe- 3s/iro-xe-3s-book/iro-ipfrr-lfa.html

Question No : 297 - Topic 3 How many bytes comprise the system ID within an IS-IS NET? A. 4 bytes B. 6 bytes C. 8 bytes D. 16 bytes E. 20 bytes

Answer : B Explanation: Routers are identified with NETs of 8 to 20 bytes. ISO/IEC 10589 distinguishes only three fields in the NSAP address format: a variable-length area address beginning with a single octet, a system ID, and a 1-byte n-selector. Cisco implements a fixed length of 6 bytes for the system ID, which is like the OSPF router ID. Reference: http://www.cisco.com/en/US/products/ps6599/products_white_paper09186a00800a3e6f.sh tml

Question No : 173 - Topic 3 Which statement about the overload bit in IS-IS is true? A. The IS-IS adjacencies on the links for which the overload bit is set are brought down. B. Routers running SPF ignore LSPs with the overload bit set and hence avoid blackholing traffic. C. A router setting the overload bit becomes unreachable to all other routers in the IS-IS area. D. The overload bit in IS-IS is used only for external prefixes.

Answer : B Explanation: The OL bit is used to prevent unintentional blackholing of packets in BGP transit networks. Due to the nature of these protocols, IS-IS and OSPF converge must faster than BGP. Thus there is a possibility that while the IGP has converged, IBGP is still learning the routes. In that case if other IBGP routers start sending traffic towards this IBGP router that has not yet completely converged it will start dropping traffic. This is because it isnt yet aware of the complete BGP routes. OL bit comes handy in such situations. When a new IBGP neighbor is added or a router restarts, the IS-IS OL bit is set. Since directly connected (including loopbacks) addresses on an overloaded router are considered by other routers, IBGP can be bought up and can begin exchanging routes. Other routers will not use this router for transit traffic and will route the packets out through an alternate path. Once BGP has converged, the OL bit is cleared and this router can begin forwarding transit traffic. Reference: https://routingfreak.wordpress.com/category/ospf-vs-is-is/

Question No : 242 - Topic 3 Which BGP feature enables you to install a backup path in the forwarding table? A. soft reconfiguration B. prefix independent convergence C. route refresh D. synchronization

Answer : B Explanation: To install a backup path into the forwarding table and provide prefix independent convergence (PIC) in case of a PE-CE link failure, use the additional-paths install backup command in an appropriate address family configuration mode. To prevent installing the backup path, use the no form of this command. To disable prefix independent convergence, use the disable keyword. Reference: http://www.cisco.com/c/en/us/td/docs/routers/crs/software/crs_r4- 2/routing/command/reference/b_routing_cr42crs/b_routing_cr42crs_chapter_01.html

Question No : 270 - Topic 3 When deploying redundant route reflectors in BGP, which attribute can you configure on the route reflector to allow routes to be identified as belonging to the same group? A. ROUTER_ID B. CLUSTER_ID C. ORIGINATOR_ID D. PEER_GROUP

Answer : B Explanation: Together, a route reflector and its clients form a cluster. When a single route reflector is deployed in a cluster, the cluster is identified by the router ID of the route reflector. The bgp cluster-id command is used to assign a cluster ID to a route reflector when the cluster has one or more route reflectors. Multiple route reflectors are deployed in a cluster to increase redundancy and avoid a single point of failure. When multiple route reflectors are configured in a cluster, the same cluster ID is assigned to all route reflectors. This allows all route reflectors in the cluster to recognize updates from peers in the same cluster and reduces the number of updates that need to be stored in BGP routing tables. Reference: http://ieoc.com/forums/t/5326.aspx

Question No : 281 - Topic 3 Which option describes the effect of the OSPF default-information originate always command? A. It creates a stub area. B. It configures the device to advertise a default route regardless of whether it exists in the routing table. C. It configures the device to automatically redistribute a default route. D. It adds a static default route to the device configuration.

Answer : B Explanation: default-information originate To generate a default external route into an Open Shortest Path First (OSPF) routing domain, use the default-information originate command in router configuration mode. To disable this feature, use the no form of this command. ] [ ] Syntax Description always (Optional) Always advertises the default route regardless of whether the software has a default route. Reference: http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/ipv6/command/ipv6-cr- book/ipv6-d2.html

Question No : 143 - Topic 3 Which statement describes the difference between a stub area and a totally stub area? A. The ABR advertises a default route to a totally stub area and not to a stub area. B. Stub areas do not allow LSA types 4 and 5, while totally stub areas do not allow LSA types 3, 4, and 5. C. Totally stub areas allow limited external routes in the area via a special type 7 LSA, while stub areas do not. D. Stub areas do not allow external LSAs, ASBR summary LSAs, or summary LSAs with the exception of a default route originated by the ABR via a summary LSA.

Answer : B Explanation: ✑ Standard areas can contain LSAs of type 1, 2, 3, 4, and 5, and may contain an ASBR. The backbone is considered a standard area. ✑ Stub areas can contain type 1, 2, and 3 LSAs. A default route is substituted for external routes. ✑ Totally stubby areas can only contain type 1 and 2 LSAs, and a single type 3 LSA. The type 3 LSA describes a default route, substituted for all external and inter-area routes. ✑ Not-so-stubby areas implement stub or totally stubby functionality yet contain an ASBR. Type 7 LSAs generated by the ASBR are converted to type 5 by ABRs to be flooded to the rest of the OSPF domain. Reference: http://packetlife.net/blog/2008/jun/24/ospf-area-types/

Question No : 292 - Topic 3 Which two modes of operation does BFD support? (Choose two.) A. synchronous mode B. asynchronous mode C. demand mode D. echo mode E. aggressive mode F. passive mode

Answer : B,C Explanation: A session may operate in one of two modes: asynchronous mode and demand mode. In asynchronous mode, both endpoints periodically send Hello packets to each other. If a number of those packets are not received, the session is considered down. In demand mode, no Hello packets are exchanged after the session is established; it is assumed that the endpoints have another way to verify connectivity to each other, perhaps on the underlying physical layer. However, either host may still send Hello packets if needed. Reference: http://en.wikipedia.org/wiki/Bidirectional_Forwarding_Detection

Question No : 187 - Topic 3 Which two statements about the function of a PIM designated router are true? (Choose two.) A. It forwards multicast traffic from the source into the PIM network. B. It registers directly connected sources to the PIM rendezvous point. C. It sends PIM Join/Prune messages for directly connected receivers. D. It sends IGMP queries. E. It sends PIM asserts on the interfaces of the outgoing interface list.

Answer : B,C Explanation: In PIM ASM and SSM modes, the software chooses a designated router (DR) from the routers on each network segment. The DR is responsible for forwarding multicast data for specified groups and sources on that segment. In ASM mode, the DR is responsible for unicasting PIM register packets to the RP. When a DR receives an IGMP membership report from a directly connected receiver, the shortest path is formed to the RP, which may or may not go through the DR. The result is a shared tree that connects all sources transmitting on the same multicast group to all receivers of that group. In SSM mode, the DR triggers (*, G) or (S, G) PIM join messages toward the RP or the source. The path from the receiver to the source is determined hop by hop. The source must be known to the receiver or the DR. Reference: http://www.cisco.com/c/en/us/td/docs/switches/datacenter/sw/5_x/nx- os/multicast/configuration/guide/n7k_multic_cli_5x/pim.html#wp1054047

Question No : 155 - Topic 3 Which two options are reasons to manipulate the delay metric instead of the bandwidth metric for EIGRP routing? (Choose two.) A. Because the delay metric provides better handling for bursty traffic B. Because manipulating the bandwidth metric can also affect QoS C. Because manipulating the bandwidth affects only a particular path D. Because changes to the delay metric are propagated to all neighbors on a segment

Answer : B,D Explanation: Using the bandwidth to influence EIGRP paths is discouraged for two reasons: ✑ Changing the bandwidth can have impact beyond affecting the EIGRP metrics. For example, quality of service (QoS) also looks at the bandwidth on an interface. ✑ EIGRP throttles to use 50 percent of the configured bandwidth. Lowering the bandwidth can cause problems like staving EIGRP neighbors from getting hello packets because of the throttling back. Because changes to the delay metric are propagated to all downstream routers, changing the interface delay parameter is the preferred method of influencing path selection Reference: http://www.cisco.com/c/en/us/support/docs/ip/enhanced-interior-gateway- routing-protocol-eigrp/13673-14.html

Question No : 285 - Topic 3 Which two configuration changes should be made on the OTP interface of an EIGRP OTP route reflector? (Choose two.) A. passive-interface B. no split-horizon C. no next-hop-self D. hello-interval 60, hold-time 180

Answer : B,C Explanation: The EIGRP Over the Top feature enables a single end-to-end Enhanced Interior Gateway Routing Protocol (EIGRP) routing domain that is transparent to the underlying public or private WAN transport that is used for connecting disparate EIGRP customer sites. When an enterprise extends its connectivity across multiple sites through a private or a public WAN connection, the service provider mandates that the enterprise use an additional routing protocol, typically the Border Gateway Protocol (BGP), over the WAN links to ensure end-to-end routing. The use of an additional protocol causes additional complexities for the enterprise, such as additional routing processes and sustained interaction between EIGRP and the routing protocol to ensure connectivity, for the enterprise. With the EIGRP Over the Top feature, routing is consolidated into a single protocol (EIGRP) across the WAN. Perform this task to configure a customer edge (CE) device in a network to function as an EIGRP Route Reflector: 1. enable 2. configure terminal 3. router eigrp virtual-name 4. address-family ipv4 unicast autonomous-system as-number 5. af-interface interface-type interface-number 6. no next-hop-self 7. no split-horizon 8. exit 9. remote-neighbors source interface-type interface-number unicast-listen lisp-encap 10. network ip-address 11. end Note. Use no next-hop-self to instruct EIGRP to use the received next hop and not the local outbound interface address as the next hop to be advertised to neighboring devices. If no next-hop-self is not configured, the data traffic will flow through the EIGRP Route Reflector. Reference: http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_eigrp/configuration/xe- 3s/ire-xe-3s-book/ire-eigrp-over-the-top.html

Question No : 311 - Topic 3 Which two technologies are supported by EIGRP? (Choose two.) A. clear-text authentication B. MD5 authentication C. stub routing D. multiple areas

Answer : B,C Explanation: The IP Enhanced IGRP Route Authentication feature provides MD5 authentication of routing updates from the EIGRP routing protocol. The MD5 keyed digest in each EIGRP packet prevents the introduction of unauthorized or false routing messages from unapproved sources. The EIGRP stub routing feature improves network stability, reduces resource utilization, and simplifies the stub device configuration. Stub routing is commonly used in hub-and-spoke network topologies. In a hub-and-spoke network, one or more end (stub) networks are connected to a remote device (the spoke) that is connected to one or more distribution devices (the hub). The remote device is adjacent to one or more distribution devices. The only route for IP traffic to reach the remote device is through a distribution device. References: http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_eigrp/configuration/15-s/ire-15-s- book/ire-rte-auth.html http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_eigrp/configuration/15-s/ire-15-s- book/ire-eigrp-stub-rtg.html

Question No : 225 - Topic 3 Which two statements about the function of the stub feature in EIGRP are true? (Choose two.) A. It stops the stub router from sending queries to peers. B. It stops the hub router from sending queries to the stub router. C. It stops the stub router from propagating dynamically learned EIGRP prefixes to the hub routers. D. It stops the hub router from propagating dynamically learned EIGRP prefixes to the stub routers. question_answerVIEW ANSWER SHOW COMMENTS 0

Answer : B,C Explanation: When using the EIGRP Stub Routing feature, you need to configure the distribution and remote routers to use EIGRP, and to configure only the remote router as a stub. Only specified routes are propagated from the remote (stub) router. The router responds to queries for summaries, connected routes, redistributed static routes, external routes, and internal routes with the message "inaccessible." A router that is configured as a stub will send a special peer information packet to all neighboring routers to report its status as a stub router. Without the stub feature, even after the routes that are sent from the distribution router to the remote router have been filtered or summarized, a problem might occur. If a route is lost somewhere in the corporate network, EIGRP could send a query to the distribution router, which in turn will send a query to the remote router even if routes are being summarized. If there is a problem communicating over the WAN link between the distribution router and the remote router, an EIGRP stuck in active (SIA) condition could occur and cause instability elsewhere in the network. The EIGRP Stub Routing feature allows a network administrator to prevent queries from being sent to the remote router. Reference: http://www.cisco.com/c/en/us/td/docs/ios/12_0s/feature/guide/eigrpstb.html

Question No : 286 - Topic 3 Which three statements about IS-IS are true? (Choose three.) A. IS-IS can be used only in the service provider network. B. IS-IS can be used to route both IP and CLNP. C. IS-IS has three different levels of authentication: interface level, process level, and domain level. D. IS-IS is an IETF standard. E. IS-IS has the capability to provide address summarization between areas. F. IS-IS is a Cisco proprietary routing protocol. question_answerVIEW ANSWER SHOW COMMENTS

Answer : B,C,E Explanation: Intermediate System to Intermediate System (IS-IS) was designed as the routing protocol for ISO's CLNP described in IS0 10589. IS-IS is a Link State routing protocol akin to OSPF and was developed by DEC for use with DECnet Phase V. It was originally thought that TCP/IP would gradually make way for the seven layer OSI architecture so an enhancement to IS-IS was developed called Integrated IS-IS also known as Dual IS-IS that could route both Connectionless-Mode Network Service (CLNS) as well as IP. Cisco IOS supports IS-IS authentication on 3 different levels; between neighbors, area- wide, and domain-wide, where each can be used by themselves or together. summary-address address mask {level-1 | level-1-2 | level-2} is used to configure IP address summarization. References: http://www.rhyshaden.com/isis.htm http://mynetworkingwiki.com/index.php/Configuring_IS-IS

Question No : 319 - Topic 3 Which two statements about the BGP community attribute are true? (Choose two.) A. Routers send the community attribute to all BGP neighbors automatically. B. A router can change a received community attribute before advertising it to peers. C. It is a well-known, discretionary BGP attribute. D. It is an optional transitive BGP attribute. E. A prefix can support only one community attribute.

Answer : B,D Explanation: A community is a group of prefixes that share some common property and can be configured with the BGP community attribute. The BGP Community attribute is an optional transitive attribute of variable length. The attribute consists of a set of four octet values that specify a community. The community attribute values are encoded with an Autonomous System (AS) number in the first two octets, with the remaining two octets defined by the AS. A prefix can have more than one community attribute. A BGP speaker that sees multiple community attributes in a prefix can act based on one, some or all the attributes. A router has the option to add or modify a community attribute before the router passes the attribute on to other peers. Reference: http://www.cisco.com/c/en/us/support/docs/ip/border-gateway-protocol-bgp/28784-bgp- community.html

Question No : 248 - Topic 3 What is the function of an EIGRP sequence TLV packet? A. to acknowledge a set of sequence numbers during the startup update process B. to list the peers that should listen to the next multicast packet during the reliable multicast process C. to list the peers that should not listen to the next multicast packet during the reliable multicast process D. to define the initial sequence number when bringing up a new peer

Answer : C Explanation: EIGRP sends updates and other information between routers using multicast packets to 224.0.0.10. For example in the topology below, R1 made a change in the topology and it needs to send updates to R2 & R3. It sends multicast packets to EIGRP multicast address 224.0.0.10. Both R2 & R3 can receive the updates and acknowledge back to R1 using unicast. Simple, right? But what if R1 sends out updates, only R2 replies but R3 never does? In the case a router sends out a multicast packet that must be reliable delivered (like in this case), an EIGRP process will wait until the RTO (retransmission timeout) period has passed before beginning a recovery action. This period is calculated from the SRTT (smooth round-trip time). After R1 sends out updates it will wait for this period to expire. Then it makes a list of all the neighbors from which it did not receive an Acknowledgement (ACK). Next it sends out a packet telling these routers stop listening to multicast until they are been notified that it is safe again. Finally the router will begin sending unicast packets with the information to the routers that didnt answer, continuing until they are caught up. In our example the process will be like this: 1. R1 sends out updates to 224.0.0.10 2. R2 responds but R3 does not 3. R1 waits for the RTO period to expire 4. R1 then sends out an unreliable-multicast packet, called a sequence TLV (Type-Length- Value) packet, which tells R3 not to listen to multicast packets any more 5. R1 continues sending any other muticast traffic it has and delivering all traffic, using unicast to R3, until it acknowledges all the packets 6. Once R3 has caught up, R1 will send another sequence TLV, telling R3 to begin listening to multicast again. The sequence TLV packet contains a list of the nodes that should not listen to multicast packets while the recovery takes place. But notice that the TLV packet in step 6 does not contain any nodes in the list. Note. In the case R3 still does not re

Question No : 241 - Topic 3 Which option describes the purpose of the leak-map keyword in the command eigrp stub connected leak-map EigrpLeak? A. It allows the specified static routes to be advertised. B. It allows exceptions to the route summarization that is configured. C. It allows specified EIGRP-learned routes to be advertised. D. It restricts specified connected routes from being advertised.

Answer : C Explanation: ExamplE. eigrp stub leak-map Command In the following example, the eigrp stub command is issued with the leak-map name keyword-argument pair to configure the device to reference a leak map that identifies routes to be advertised that would have been suppressed otherwisE. Device(config)# router eigrp 1 Device(config-router)# network 10.0.0.0 Device(config-router)# eigrp stub leak-map map1 Reference: http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_eigrp/configuration/15- mt/ire-15-mt-book/ire-eigrp-stub-rtg.html#GUID-FB899CA9-E9DE-48D8-8048- C971179E4E24

Question No : 221 - Topic 3 Which regular expression will match prefixes that originated from AS200? A. ^$ B. ^200_ C. _200$ D. ^200) E. _200_

Answer : C Explanation: Example on how to deny all prefixes originated in Autonomous System 200 router bgp 100 neighbor 10.1.1.1 remote-as 65535 neighbor 10.1.1.1 route-map map1 in ! route-map map1 permit 10 match as-path 1 ! ip as-path access-list 5 deny _200$ ip as-path access-list 5 permit .* Reference: http://www.cisco.com/c/en/us/td/docs/ios/termserv/configuration/guide/12_4t/tsv_12_4t_bo ok/tsv_reg_express.html

Question No : 169 - Topic 3 How does having an EIGRP feasible successor speed up convergence? A. EIGRP sends queries only if there is a feasible successor, which decreases the number of routers that are involved in convergence. B. EIGRP sends queries only if there is not a feasible successor, which causes less control traffic to compete with data. C. EIGRP immediately installs the loop-free alternative path in the RIB. D. EIGRP preinstalls the feasible successor in the RIB in all cases, which causes traffic to switch more quickly. question_answerVIEW ANSWER SHOW COMMENTS 0

Answer : C Explanation: Feasible Successor ✑ A next-hop router that serves as backup to the current successor. ✑ The condition is that the said router's AD (or RD) is less than the FD of the current successor route. ✑ Once the feasible successor is selected, they are placed in the topology table. If a change in topology occurs which requires a new route, DUAL looks for the feasible successor and uses it as new route immediately, resulting in fast convergence. Reference: http://routemyworld.com/2008/07/page/2/

Question No : 256 - Topic 3 Which option describes how a router responds if LSA throttling is configured and it receives the identical LSA before the interval is set? A. The LSA is added to the OSPF database and a notification is sent to the sending router to slow down its LSA packet updates. B. The LSA is added to the OSPF database. C. The LSA is ignored. D. The LSA is ignored and a notification is sent to the sending router to slow down its LSA packet updates.

Answer : C Explanation: How OSPF LSA Throttling Works The timers throttle lsa all command controls the generation (sending) of LSAs. The first LSA is always generated immediately upon an OSPF topology change, and the next LSA generated is controlled by the minimum start interval. The subsequent LSAs generated for the same LSA are rate-limited until the maximum interval is reached. The "same LSA" is defined as an LSA instance that contains the same LSA ID number, LSA type, and advertising router ID. The timers LSA arrival command controls the minimum interval for accepting the same LSA. If an instance of the same LSA arrives sooner than the interval that is set, the LSA is dropped. It is recommended that the arrival interval be less than or equal to the hold-time interval of the timers throttle lsa all command. Reference: http://www.cisco.com/c/en/us/td/docs/ios/12_0s/feature/guide/fsolsath.html

Question No : 194 - Topic 3 Which problem can result when private AS numbers are included in advertisements that are sent to the global Internet BGP table? A. The prefixes sent with private AS numbers are always discarded on the Internet. B. The prefixes sent with private AS numbers are always tagged as invalid on the Internet. C. The prefixes sent with private AS numbers lack uniqueness, which can lead to a loss of connectivity. D. The prefixes sent with private AS numbers are sometimes tagged as invalid on the Internet.

Answer : C Explanation: Private AS numbers are not meant to be used for global Internet BGP routing, as they are assigned locally and can be used by any organization. They are meant to enable BGP within a enterprise or VPN, but since these numbers can be used by any organization they are not unique and could cause connectivity loss if leaked to the Internet.

Question No : 293 - Topic 3 Which technology is an application of MSDP, and provides load balancing and redundancy between the RPs? A. static RP B. PIM BSR C. auto RP D. anycast RP question_answerVIEW ANSWER

Answer : D Explanation: Using Anycast RP is an implementation strategy that provides load sharing and redundancy in Protocol Independent Multicast sparse mode (PIM-SM) networks. Anycast RP allows two or more rendezvous points (RPs) to share the load for source registration and the ability to act as hot backup routers for each other. Multicast Source Discovery Protocol (MSDP) is the key protocol that makes Anycast RP possible. Reference: www.cisco.com/c/en/us/td/docs/ios/solutions_docs/ip_multicast/White_papers/anycast.html

Question No : 190 - Topic 3 What are the minimal configuration steps that are required to configure EIGRP HMAC- SHA2 authentication? A. classic router mode, interface XX, authentication mode hmac-sha-256 <password> B. named router mode, address-family statement, authentication mode hmac-sha-256 <password> C. named router mode, address-family statement, af-interface default, authentication mode hmac-sha-256 <password> D. named router mode, address-family statement, authentication mode hmac-sha-256 <password>

Answer : C Explanation: The example below shows how to configure EIGRP HMAC-SHA2 on Cisco router: Device(config)# router eigrp name1 Device(config-router)# address-family ipv4 autonomous-system 45000 Device(config-router-af)# af-interface ethernet 0/0 Device(config-router-af-interface)# authentication mode hmac-sha-256 0 password1 Device(config-router-af-interface)# end Reference: http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_eigrp/configuration/15- sy/ire-15-sy-book/ire-sha-256.html

Question No : 168 - Topic 3 What is the function of the command ip pim autorp listener? A. It allows a border PIM sparse mode router to accept autorp information from another autonomous system. B. It allows the mapping agents to accept autorp information from the PIM rendezvous point. C. It allows the routers to flood the autorp information in a sparse-mode-only network. D. It allows a BSR to accept autorp information and translate it into BSR messages.

Answer : C Explanation: To cause IP multicast traffic for the two Auto-RP groups 224.0.1.39 and 224.0.1.40 to be Protocol Independent Multicast (PIM) dense mode flooded across interfaces operating in PIM sparse mode, use the ip pim autorp listener command in global configuration mode. To disable this feature, use the no form of this command. Reference: http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/ipmulti/command/imc-cr- book/imc_i3.html#wp3085748429

Question No : 227 - Topic 3 Consider a network that mixes link bandwidths from 128 kb/s to 40 Gb/s. Which value should be set for the OSPF reference bandwidth? A. Set a value of 128. B. Set a value of 40000. C. Set a manual OSPF cost on each interface. D. Use the default value. E. Set a value of 40000000. F. Set a value of 65535

Answer : C Explanation: Unlike the metric in RIP which is determined by hop count and EIGRPs crazy mathematical formulated metric, OSPF is a little more simple. The default formula to calculate the cost for the OSPF metric is (10^8/BW). By default the metrics reference cost is 100Mbps, so any link that is 100Mbps will have a metric of 1. a T1 interface will have a metric of 64 so in this case if a router is trying to get to a FastEthernet network on a router that is through a T1 the metric would be 65 (64 +1). You do however have the ability to statically specify a metric on a per interface basis by using the ip ospf cost # where the cost is an integer between 1-65535. So the big question is why would you want to statically configure a metric? The biggest advantage of statically configuring an OSPF metric on an interface is to manipulate which route will be chosen dynamically via OSPF. In a nut shell its like statically configuring a dynamic protocol to use a specific route. It should also be used when the interface bandwidths vary greatly (some very low bandwidth interfaces and some very high speed interfaces on the same router).

Question No : 185 - Topic 3 Which statement about passive interfaces is true? A. The interface with the OSPF passive interface configuration appears as a not-so-stubby network. B. The interface with the EIGRP passive interface configuration ignores routes after the exchange of hello packets. C. The interface with the IS-IS passive interface configuration sends the IP address of that interface in the link-state protocol data units. D. Passive interface can be configured on the interface for IS-IS.

Answer : C Explanation: With IS-IS, passive interfaces are used to prevent unnecessary LSA packets out that interface, but the IP address of passive interfaces are still included in updates going out the other interfaces. This behavior is what enables the best practice of configuring loopback interfaces as passive, but still having the loopback be reachable.

Question No : 204 - Topic 3 Which two statements are true about IS-IS? (Choose two.) A. IS-IS DIS election is nondeterministic. B. IS-IS SPF calculation is performed in three phases. C. IS-IS works over the data link layer, which does not provide for fragmentation and reassembly. D. IS-IS can never be routed beyond the immediate next hop.

Answer : C,D Explanation: IS-IS runs directly over the data link alongside IP. On Ethernet, IS-IS packets are always 802.3 frames, with LSAPs 0xFEFE while IP packets are either Ethernet II frames or SNAP frames identified with the protocol number 0x800. OSPF runs over IP as protocol number 89. IS-IS runs directly over layer 2 and hence: - cannot support virtual links unless some explicit tunneling is implemented - packets are kept small so that they don't require hop-by-hop fragmentation - uses ATM/SNAP encapsulation on ATM but there are hacks to make it use VcMux encapsulation - some operating systems that support IP networking have been implemented to differentiate Layer 3 packets in kernel. Such Oss require a lot of kernel modifications to support IS-IS for IP routing. - can never be routed beyond the immediate next hop and hence shielded from IP spoofing and similar Denial of Service attacks. Reference: https://tools.ietf.org/html/draft-bhatia-manral-diff-isis-ospf-00

Question No : 183 - Topic 3 Which two statements are true about IPv6 multicast? (Choose two.) A. Receivers interested in IPv6 multicast traffic use IGMPv6 to signal their interest in the IPv6 multicast group. B. The PIM router with the lowest IPv6 address becomes the DR for the LAN. C. An IPv6 multicast address is an IPv6 address that has a prefix of FF00::/8. D. The IPv6 all-routers multicast group is FF02:0:0:0:0:0:0:2.

Answer : C,D Explanation: Multicast addresses in IPv6 have the prefix ff00::/8. Well-known IPv6 multicast addresses Address Description ff02::1 All nodes on the local network segment ff02::2 All routers on the local network segment Reference: http://en.wikipedia.org/wiki/Multicast_address

Question No : 313 - Topic 3 Which two DHCP messages are always sent as broadcast? (Choose two.) A. DHCPOFFER B. DHCPDECLINE C. DHCPRELEASE D. DHCPREQUEST E. DHCPDISCOVER

Answer : D,E Explanation: DHCP discovery The client broadcasts messages DHCPDISCOVER on the network subnet using the destination address 255.255.255.255 or the specific subnet broadcast address. DHCP request In response to the DHCP offer, the client replies with a DHCP request, broadcasts to the server, requesting the offered address. A client can receive DHCP offers from multiple servers, but it will accept only one DHCP offer. Reference: http://en.wikipedia.org/wiki/Dynamic_Host_Configuration_Protocol

Question No : 289 - Topic 3 For which two conditions is Cisco Express Forwarding recursion disabled by default when the BGP Prefix Independent Convergence functionality is enabled? (Choose two.) A. next hops learned with a /24 mask B. next hops learned with any mask shorter than /32 C. next hops learned with a /32 mask D. next hops that are directly connected

Answer : C,D Explanation: Recursion is the ability to find the next longest matching path when the primary path goes down. When the BGP PIC feature is not installed, and if the next hop to a prefix fails, Cisco Express Forwarding finds the next path to reach the prefix by recursing through the FIB to find the next longest matching path to the prefix. This is useful if the next hop is multiple hops away and there is more than one way of reaching the next hop. However, with the BGP PIC feature, you may want to disable Cisco Express Forwarding recursion for the following reasons: ✑ Recursion slows down convergence when Cisco Express Forwarding searches all the FIB entries. ✑ BGP PIC Edge already precomputes an alternate path, thus eliminating the need for Cisco Express Forwarding recursion. When the BGP PIC functionality is enabled, Cisco Express Forwarding recursion is disabled by default for two conditions: ✑ For next hops learned with a /32 network mask (host routes) ✑ For next hops that are directly connected For all other cases, Cisco Express Forwarding recursion is enabled. Reference: http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_bgp/configuration/xe- 3s/irg-xe-3s-book/irg-bgp-mp-pic.html

Question No : 163 - Topic 3 EIGRP allows configuration of multiple MD5 keys for packet authentication to support easy rollover from an old key to a new key. Which two statements are true regarding the usage of multiple authentication keys? (Choose two.) A. Received packets are authenticated by the key with the smallest key ID. B. Sent packets are authenticated by all valid keys, which means that each packet is replicated as many times as the number of existing valid keys. C. Received packets are authenticated by any valid key that is chosen. D. Sent packets are authenticated by the key with the smallest key ID.

Answer : C,D Explanation: Suppose two routers are connected with each other via Fa0/0 interfaces and they are configured to authenticate via MD5. Below is a simple configuration on both routers so that they will work: Router1(config)#key chain KeyChainR1 Router1(config-keychain)#key 1 Router1(config-keychain-key)#key-string FirstKey Router1(config-keychain-key)#key 2 Router1(config-keychain-key)#key-string SecondKey Router2(config)#key chain KeyChainR2 Router2(config-keychain)#key 1 Router2(config-keychain-key)#key-string FirstKey Router2(config-keychain-key)#key 2 Router2(config-keychain-key)#key-string SecondKey Apply these key chains to R1 & R2: Router1(config)#interface fastEthernet 0/0 Router1(config-if)#ip authentication mode eigrp 1 md5 Router1(config-if)#ip authentication key-chain eigrp 1 KeyChainR1 Router2(config)#interface fastEthernet 0/0 Router2(config-if)#ip authentication mode eigrp 1 md5 Router2(config-if)#ip authentication key-chain eigrp 1 KeyChainR2 There are some rules to configure MD5 authentication with EIGRP: + The key chain names on two routers do not have to match (in this case the name KeyChainR1 & KeyChainR2 do not match) + The key number and key-string on the two potential neighbors must match (for example key 1 & key-string FirstKey must match on key 1 & key-string FirstKey of neighboring router) Also some facts about MD5 authentication with EIGRP + When sending EIGRP messages the lowest valid key number is used -> D is correct. + When receving EIGRP messages all currently configured valid keys are verified but the lowest valid one will be used -> Although answer C does not totally mention like that but it is the most suitable answer because A and B are totally wrong. Answer A is not correct because we need valid key to authenticate. As mentioned above, although answer C is not totally correct but it puts some light on why answer B is not correct: each packet is NOT replicated as many times as the number of existing valid keys. All currently configur

Question No : 228 - Topic 3 Which two statements about the command distance bgp 90 60 120 are true? (Choose two.) A. Implementing the command is a Cisco best practice. B. The external distance it sets is preferred over the internal distance. C. The internal distance it sets is preferred over the external distance. D. The local distance it sets may conflict with the EIGRP administrative distance. E. The internal distance it sets may conflict with the EIGRP administrative distance. F. The local distance it sets may conflict with the RIP administrative distance.

Answer : C,F Explanation: To allow the use of external, internal, and local administrative distances that could be a better route than other external, internal, or local routes to a node, use the distance bgp command in address family or router configuration mode. To return to the default values, use the no form of this command. no distance bgp ✑ Syntax Description external-distance Administrative distance for BGP external routes. External routes are routes for which the best path is learned from a neighbor external to the autonomous system. Accept table values are from 1 to 255. The default is 20. Routes with a distance of 255 are not installed in the routing table. internal-distance Administrative distance for BGP internal routes. Internal routes are those routes that are learned from another BGP entity within the same autonomous system. Accept table values are from 1 to 255. The default is 200. Routes with a distance of 255 are not installed in the routing table. local-distance Administrative distance for BGP local routes. Local routes are those networks listed with a network router configuration command, often as back doors, for that router or for networks that are being redistributed from another process. Accept table values are from 1 to 255. The default is 200. Routes with a distance of 255 are not installed in the routing table. Defaults : 20 : 200 : 200 In this case, the internal distance is 60 and the external is 90, and the local distance is 120 (same as RIP). Reference: http://www.cisco.com/c/en/us/td/docs/ios/12_2/iproute/command/reference/fiprrp_r/1rfbgp1. html#wp1113874

Question No : 278 - Topic 3 Which statement about OSPF multiaccess segments is true? A. The designated router is elected first. B. The designated and backup designated routers are elected at the same time. C. The router that sent the first hello message is elected first. D. The backup designated router is elected first.

Answer : D Explanation: According to the RFC, the BDR is actually elected first, followed by the DR. The RFC explains why: The reason behind the election algorithms complexity is the desire for an orderly transition from Backup Designated Router to Designated Router, when the current Designated Router fails. This orderly transition is ensured through the introduction of hysteresis: no new Backup Designated Router can be chosen until the old Backup accepts its new Designated Router responsibilities. The above procedure may elect the same router to be both Designated Router and Backup Designated Router, although that router will never be the calculating router (Router X) itself. Reference: http://www.ietf.org/rfc/rfc2328.txt Page 76

Question No : 153 - Topic 3 When BGP route reflectors are used, which attribute ensures that a routing loop is not created? A. weight B. local preference C. multiexit discriminator D. originator ID

Answer : D Explanation: As the iBGP learned routes are reflected, routing information may loop. The route reflector model has the following mechanisms to avoid routing loops: Originator ID is an optional, nontransitive BGP attribute. It is a 4-byte attributed created by a route reflector. The attribute carries the router ID of the originator of the route in the local autonomous system. Therefore, if a misconfiguration causes routing information to come back to the originator, the information is ignored. Cluster-list is an optional, nontransitive BGP attribute. It is a sequence of cluster IDs that the route has passed. When a route reflector reflects a route from its clients to nonclient peers, and vice versa, it appends the local cluster ID to the cluster-list. If the cluster-list is empty, a new cluster-list is created. Using this attribute, a route reflector can identify if routing information is looped back to the same cluster due to misconfiguration. If the local cluster ID is found in the cluster-list, the advertisement is ignored. Reference: http://www.cisco.com/c/en/us/td/docs/ios/12_2/ip/configuration/guide/fipr_c/1cfbgp.html

Question No : 322 - Topic 3 Which statement describes the BGP add-path feature? A. It allows for installing multiple IBGP and EBGP routes in the routing table. B. It allows a network engineer to override the selected BGP path with an additional path created in the config. C. It allows BGP to provide backup paths to the routing table for quicker convergence. D. It allows multiple paths for the same prefix to be advertised.

Answer : D Explanation: BGP routers and route reflectors (RRs) propagate only their best path over their sessions. The advertisement of a prefix replaces the previous announcement of that prefix (this behavior is known as an implicit withdraw). The implicit withdraw can achieve better scaling, but at the cost of path diversity. Path hiding can prevent efficient use of BGP multipath, prevent hitless planned maintenance, and can lead to MED oscillations and suboptimal hot-potato routing. Upon nexthop failures, path hiding also inhibits fast and local recovery because the network has to wait for BGP control plane convergence to restore traffic. The BGP Additional Paths feature provides a generic way of offering path diversity; the Best External or Best Internal features offer path diversity only in limited scenarios. The BGP Additional Paths feature provides a way for multiple paths for the same prefix to be advertised without the new paths implicitly replacing the previous paths. Thus, path diversity is achieved instead of path hiding. Reference: http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_bgp/configuration/xe- 3s/irg-xe-3s-book/irg-additional-paths.html

Question No : 230 - Topic 3 Which command do you use to connect a dense-mode domain to a sparse-mode multicast domain? A. none, because there is no such command B. ip pim spt-threshold infinity C. ip pim register dense-mode D. ip pim dense-mode proxy-register

Answer : D Explanation: For IP PIM multicast, Cisco recommends Sparse-Mode over Dense-Mode. In the midst of our network migration, we have a new network operating in Sparse-Mode with Anycast rendezvous point (RP) but our existing network is still operating in Dense-Mode. To bridge two different modes across both PIM domains, we should use the ip pim dense-mode proxy-register command on the interface leading toward the bordering dense mode region. This configuration will enable the border router to register traffic from the dense mode region (which has no concept of registration) with the RP in the sparse mode domain. Reference: http://networkerslog.blogspot.com/2010/12/bridging-dense-mode-pim-to- sparse-mode.html

Question No : 178 - Topic 3 Which field is specific to the OPSFv3 packet header, as opposed to the OSPFv2 packet header? A. checksum B. router ID C. AuType D. instance ID question_answerVIEW ANSWER

Answer : D Explanation: In OSPFv3, Instance ID is a new field that is used to have multiple OSPF process instance per link. By default it is 0 and for any additional instance it is increased, instance ID has local link significance only. OSPFv3 routers will only become neighbors if the instanceIDs match. It is thus possible to have multiple routers on a broadcast domain and all run Ospfv3 but not all of them becoming neighbors. Reference: https://supportforums.cisco.com/document/97766/comparing-ospfv3-ospfv2- routing-protocol

Question No : 263 - Topic 3 Which measure does IS-IS use to avoid sending traffic with a wrong MTU configuration? A. IS-IS does not protect from MTU mismatch. B. MTU value is communicated in IS-IS Sequence Number PDUs (SNP), and IS-IS adjacency is not established if an MTU mismatch is detected. C. IS-IS uses path MTU discovery as specified in RFC 1063. D. IS-IS uses padding of hello packets to full MTU.

Answer : D Explanation: Intermediate System-to-Intermediate System (IS-IS) hellos are padded to the full maximum transmission unit (MTU) size. The benefit of padding IS-IS Hellos (IIHs) to the full MTU is that it allows for early detection of errors due to transmission problems with large frames or due to mismatched MTUs on adjacent interfaces. Reference: http://www.cisco.com/c/en/us/support/docs/ip/integrated-intermediate-system- to-intermediate-system-is-is/47201-isis-mtu.html

Question No : 199 - Topic 3 Which type of OSPF packet is an OSPF link state update packet? A. type 1 B. type 2 C. type 3 D. type 4 E. type 5

Answer : D Explanation: Link State Update packets are OSPF packet type 4. These packets implement the flooding of link state advertisements. Each Link State Update packet carries a collection of link state advertisements one hop further from its origin. Several link state advertisements may be included in a single packet. Reference: http://www.freesoft.org/CIE/RFC/1583/107.htm

Question No : 167 - Topic 3 Which statement about BGP and diverse path advertisement is true? A. The BGP best-path selection must be disabled. B. The BGP best-path selection algorithm has been changed to always ignore the IGP metric. C. The BGP best-path selection algorithm has been changed so that two BGP paths can be flagged as best in the BGP table. D. The BGP best-path selection algorithm has not been changed. E. The BGP best-path selection is disabled for BGP routes for which the feature is enabled.

Answer : D Explanation: The BGP Diverse Path Using a Diverse-Path Route Reflector feature allows BGP to distribute an alternative path other than the best path between BGP speakers when route reflectors are deployed. This additional path is added to the best-path, and the best path algorithm still remains unchanged.

Question No : 152 - Topic 3 What does a nonzero forwarding address indicate in a type-5 LSA? A. It indicates that this link-state ID is eligible for ECMP. B. It indicates that this router should have an OSPF neighbor relationship with the forwarding address before using this link-state ID. C. It indicates that the receiving router must check that the next hop is reachable in its routing table before using this link-state ID. D. It indicates that traffic can be directly routed to this next hop in shared segment scenarios where the external route source is directly connected.

Answer : D Explanation: The value of the forwarding address specified by the autonomous system boundary router (ASBR) can be either 0.0.0.0 or non-zero. The 0.0.0.0 address indicates that the originating router (the ASBR) is the next hop. The forwarding address is determined by these conditions: ✑ The forwarding address is set to 0.0.0.0 if the ASBR redistributes routes and OSPF is not enabled on the next hop interface for those routes. ✑ These conditions set the forwarding address field to a non-zero address: ASBR's next hop interface address falls under the network range specified in the router ospf command. Reference: http://www.cisco.com/c/en/us/support/docs/ip/open-shortest-path-first- ospf/13682-10.html

Question No : 198 - Topic 3 Which three EIGRP packet types are valid? (Choose three.) A. open B. notification C. keep-alive D. hello E. query F. reply

Answer : D,E,F Explanation: EIGRP uses the following packet types: hello and acknowledgment, update, and query and reply. Hello packets are multicast for neighbor discovery/recovery and do not require acknowledgment. An acknowledgment packet is a hello packet that has no data. Acknowledgment packets contain a nonzero acknowledgment number and always are sent by using a unicast address. Update packets are used to convey reachability of destinations. When a new neighbor is discovered, unicast update packets are sent so that the neighbor can build up its topology table. In other cases, such as a link-cost change, updates are multicast. Updates always are transmitted reliably. Query and reply packets are sent when a destination has no feasible successors. Query packets are always multicast. Reply packets are sent in response to query packets to instruct the originator not to recompute the route because feasible successors exist. Reply packets are unicast to the originator of the query. Both query and reply packets are transmitted reliably. Reference: http://docwiki.cisco.com/wiki/Enhanced_Interior_Gateway_Routing_Protocol

Question No : 212 - Topic 3 Which statement about a type 4 LSA in OSPF is true? A. It is an LSA that is originated by an ABR, that is flooded throughout the AS, and that describes a route to the ASBR. B. It is an LSA that is originated by an ASBR, that is flooded throughout the AS, and that describes a route to the ASBR. C. It is an LSA that is originated by an ASBR, that is flooded throughout the area, and that describes a route to the ASBR. D. It is an LSA that is originated by an ABR, that is flooded throughout the AS, and that describes a route to the ABR. E. It is an LSA that is originated by an ABR, that is flooded throughout the area, and that describes a route to the ASBR.

Answer : E Explanation: LSA Type 4 (called Summary ASBR LSA) is generated by the ABR to describe an ASBR to routers in other areas so that routers in other areas know how to get to external routes through that ASBR.

Question No : 179 - Topic 3 Which regular expression will match prefixes from the AS 200 that is directly connected to our AS? A. ^$ B. ^200) C. _200$ D. _200_ E. ^200_

Answer : E Explanation: Table 2 Commonly Used Regular Expressions Expression Meaning * Anything ^$ Locally originated routes ^100_ Learned from autonomous system 100 _100$ Originated in autonomous system 100 _100_ Any instance of autonomous system 100 ^[0-9]+$ Directly connected autonomous system paths Reference: http://www.cisco.com/c/en/us/td/docs/ios/termserv/configuration/guide/12_4t/tsv_12_4t_bo ok/tsv_reg_express.html

Question No : 226 - Topic 3 Which statement about the BGP scope of the cost community is true? A. It is shared with IBGP neighbors only. B. It is shared with IBGP neighbors and route reflectors. C. It is shared with EBGP neighbors only. D. It is shared with IBGP and EBGP neighbors. E. It is shared with IBGP and confederation peers.

Answer : E Explanation: The BGP Cost Community feature introduces the cost extended community attribute. The cost community is a non-transitive extended community attribute that is passed to internal BGP (iBGP) and confederation peers but not to external BGP (eBGP) peers. The cost community feature allows you to customize the local route preference and influence the best path selection process by assigning cost values to specific routes. Reference: http://www.cisco.com/c/en/us/td/docs/ios/12_0s/feature/guide/s_bgpcc.html

Question No : 175 - Topic 3 Which statement is true about conditional advertisements? A. Conditional advertisements create routes when a predefined condition is met. B. Conditional advertisements create routes when a predefined condition is not met. C. Conditional advertisements delete routes when a predefined condition is met. D. Conditional advertisements create routes and withhold them until a predefined condition is met. E. Conditional advertisements do not create routes, they only withhold them until a predefined condition is met.

Answer : E Explanation: The Border Gateway Protocol (BGP) conditional advertisement feature provides additional control of route advertisement, depending on the existence of other prefixes in the BGP table. Normally, routes are propagated regardless of the existence of a different path. The BGP conditional advertisement feature uses the non-exist-map and the advertise-map keywords of the neighbor advertise-map command in order to track routes by the route prefix. If a route prefix is not present in output of the non-exist-map command, then the route specified by the advertise-map command is announced. This feature is useful for multihomed networks, in which some prefixes are advertised to one of the providers only if information from the other provider is not present (this indicates a failure in the peering session or partial reachability). Reference: http://www.cisco.com/c/en/us/support/docs/ip/border-gateway-protocol- bgp/16137-cond-adv.html

Question No : 235 - Topic 3 Like OSPFv2, OSPFv3 supports virtual links. Which two statements are true about the IPv6 address of a virtual neighbor? (Choose two.) A. It is the link-local address, and it is discovered by examining the hello packets received from the virtual neighbor. B. It is the link-local address, and it is discovered by examining link LSA received by the virtual neighbor. C. It is the global scope address, and it is discovered by examining the router LSAs received by the virtual neighbor. D. Only prefixes with the LA-bit not set can be used as a virtual neighbor address. E. It is the global scope address, and it is discovered by examining the intra-area-prefix- LSAs received by the virtual neighbor. F. Only prefixes with the LA-bit set can be used as a virtual neighbor address.

Answer : E,F Explanation: OSPF for IPv6 assumes that each router has been assigned link-local unicast addresses on each of the router's attached physical links. On all OSPF interfaces except virtual links, OSPF packets are sent using the interface's associated link-local unicast address as the source address. A router learns the link-local addresses of all other routers attached to its links and uses these addresses as next-hop information during packet forwarding. On virtual links, a global scope IPv6 address MUST be used as the source address for OSPF protocol packets. The collection of intra-area-prefix-LSAs originated by the virtual neighbor is examined, with the virtual neighbor's IP address being set to the first prefix encountered with the LA-bit set. Reference: https://tools.ietf.org/html/rfc5340

Question No : 222 - Topic 3 What is the maximum number of secondary IP addresses that can be configured on a router interface? A. 1 B. 2 C. 4 D. 1024 E. 65535 F. no limit to the number of addresses

Answer : F Explanation: From IP Routing Frequently Asked Questions Q. What are the maximum number of secondary IP addesses that can be configured on a router interface? A. There are no limits on configuring secondary IP addresses on a router interface. Reference: http://www.cisco.com/c/en/us/support/docs/ip/border-gateway-protocol- bgp/28745-44.html#q21