uCertify Chapter 10

What is the administrative distance of OSPF?

110; The administrative distance (AD) is a very important parameter in a routing protocol. The lower the AD, the more trusted the route. If you have IGRP and OSPF running, by default IGRP routes would be placed in the routing table because IGRP has a lower AD of 100. OSPF has an AD of 110. RIPv1 and RIPv2 both have an AD of 120, and EIGRP is the lowest at 90.

Enhanced Interior Gateway Routing Protocol (EIGRP)

An advanced routing protocol created by Cisco, combining the advantages of link state and distance vector protocols. EIGRP has superior convergence attributes, including high operating efficiency.

What routing protocol is typically used to connect autonomous systems (ASs) on the Internet?

BGP is used to connect autonomous systems together on the Internet because of its ability to make classless routing and summarization possible. This helps to keep routing tables smaller and more efficient at the ISP core.

Which of the following routing protocols uses AS path as one of the methods to build the routing tables?

BGP; Border Gateway Protocol (BGP) attributes include the IP address to get to the next AS (the next-hop attribute) as well as an indication of how the networks at the end of the path were introduced into BGP (the origin code attribute). The AS path information is useful to construct a graph of loop-free autonomous systems and is used to identify routing policies so that restrictions on routing behavior can be enforced based on the AS path.

Which routing protocols have an administrative distance of 120? Each correct answer represents a complete solution. Choose two.

Both RIPv1 and RIPv2 have an AD of 120. EIGRP has an AD of 90 and OSPF has an AD of 110.

What is the difference between static and dynamic routing?

Dynamic routes are added automatically.; Dynamic routing protocols, like RIP, EIGRP and OSPF, automatically add the updated routes in the routing table. Static routes must be added manually.

Why would you want to use a dynamic routing protocol instead of using static routes?

Dynamic routing is typically used in today's networks because it scales to larger networks and takes less administrative work.

Which of the following are considered hybrid routing protocols? Each correct answer represents a complete solution. Choose two.

EIGRP/BGP; RIP and RIPv2 are distance vector routing protocols. OSPF and IS-IS are link state routing protocols. EIGRP uses qualities from both distance vector and link state to create a hybrid routing protocol. BGP can be used as an EGP and IGP, and hence can be considered as a hybrid routing protocol.

Which of the following protocols support VLSM, summarization, and discontiguous networking? Each correct answer represents a complete solution. Choose three.

EIGRP/OSPF/RIPv2; RIPv1 and IGRP are true distance vector routing protocols and can't do much, really—except build and maintain routing tables and use a lot of bandwidth! RIPv2, EIGRP, and OSPF build and maintain routing tables, but they also provide classless routing, which allows for VLSM, summarization, and discontiguous networking.

Which of the following is a vendor-specific FHRP protocol?

HSRP; Hot Standby Router Protocol (HSRP) is a Cisco's FHRP protocol.

VLSM (Variable Length Subnet Mask)

It allows classless routing, meaning that the routing protocol sends subnet-mask information with the route updates.

Dual stack

It allows the devices to communicate using either IPv4 or IPv6. It also allows for one-by-one upgrade of applications and devices on the network.

Distance vector protocol

It finds the best path to a remote network by judging-you guessed it-distance.

Tunneling

It involves encapsulating one type of protocol in another type of protocol for the purpose of transmitting it across a network that supports the packet type or protocol.

RIPng

It is a distance vector protocol, has a max hop count of 15, and still has the same loop avoidance mechanisms as well as using UDP port 521.

OSPFv3

It is a link state routing protocol that divides an entire internetwork or autonomous system into areas, making a hierarchy.

EIGRPv6

It is an advanced distance vector protocol that has some link state features and it gives loop-free fast convergence using DUAL.

Administrative distances

It is used to rate the trustworthiness of routing information received on one router from its neighboring router.

Routing Information Protocol (RIP)

It sends the complete routing table out to all active interfaces every 30 seconds.

RIPv2 sends out its routing table every 30 seconds just like RIPv1, but it does so more efficiently. What type of transmission does RIPv2 use to accomplish this task?

Multicasts; RIPv1 sends broadcasts every 30 seconds and has an AD of 120. RIPv2 sends multicasts (224.0.0.9) every 30 seconds and also has an AD of 120. RIPv2 sends subnet mask information with the route updates, which allows it to support classless networks and non-contiguous networks. RIPv2 also supports authentication between routers; RIPv1 does not.

Which of the following are considered link state routing protocols? Each correct answer represents a complete solution. Choose two.

OSPF/IS-IS; RIP and RIPv2 are distance vector routing protocols. OSPF and IS-IS are link state routing protocols.

Which of the following are considered distance vector routing protocols? Each correct answer represents a complete solution. Choose two.

RIP and RIPv2 are distance vector routing protocols. OSPF and IS-IS are link state routing protocols.

Which of the following uses only hop count as a metric to find the best path to a remote network?

RIP and RIPv2 use only hop count as a metric, with a maximum of 15 hops, to find the best path to a remote network.

Which IPv6 routing protocol uses UDP port 521?

RIPng; RIPng which uses UDP port 521, has many of the same features as RIPv2. It's a distance vector protocol; it has a max hop count of 15; it uses split horizon, poison reverse, and other loop-avoidance mechanisms; it still uses multicast to send its updates, but in IPv6, it uses FF02::9 for the transport address. For RIPv2, the multicast address was 224.0.0.9, so the address still has a 9 at the end in the new IPv6 multicast range.

Which of the following protocols will advertise routed IPv6 networks?

RIPng; The routing protocols that have been upgraded to advertise IPv6 routes are RIPng, OSPFv3, and EIGRPv6. IS-IS can advertise IPv6 routes as well, but no upgrade was needed for IS-IS.

Which routing protocol has a maximum hop count of 15?

RIPv1; The distance vector protocols RIPv1 and RIPv2 both have a maximum hop count of 15 (16 is unreachable). IGRP and EIGRP have a hop count of 255, and OSPF doesn't have a maximum hop count.

Which of the following describes routing convergence time?

The time required by protocols to update their forwarding tables after changes have occurred

Which is true regarding EIGRP successor routes?

They are used by EIGRP to forward traffic to a destination.; A successor route (think "successful" rather than standby or backup) is used by EIGRP to forward traffic to a destination and is stored in the routing table. It is backed up by a feasible successor route that is stored in the topology table—if one is available. Remember that all routes are in the topology table.

What EIGRP information is held in RAM and maintained through the usage of hello and update packets? Each correct answer represents a complete solution. Choose all that apply.

Topology table/Neighbor table; EIGRP holds three tables in RAM: neighbor, topology, and routing. The neighbor and topology tables are built and maintained with the use of hello packets.

RIP has a long convergence time and users have been complaining of longer response time when a router goes down and RIP needs to re-converge. What should you implement to improve convergence time on the network?

Update RIP to OSPF using link state.; Static routes may be a good solution, but they are not dynamic, and if a piece of equipment goes down, new routes to remote networks will not automatically update, so OSPF is the best answer. It will dynamically update the routing tables with faster convergence than RIP.