CCNA 2 Chapter 6
What is a quad-zero route?
* An IPv4 default static route: ip route 0.0.0.0 0.0.0.0 * The network address is 0.0.0.0 and the subnet mask is 0.0.0.0
What is another name for route summarization?
route aggregation
Which show command can check the status of router interfaces?
show ip interface brief
A network admin enters the command into R1: ip route 192.168.0.0 255.255.255.0 S0/1/0. R1 then receives a packet that is destined for 192.168.0.22/24. After finding the recently configured static route in the routing table, what does Router1 do next to process the packet?
encapsulates the packet into a frame for the WAN link and forwards the packet out the S0/1/0 interface
What is a floating static route?
static routes that provide a backup path to a primary static or dynamic route - in the event of a link failure
Why would a summarized static route be configured on a router?
to reduce the size of the routing table
Prior to CEF, what option was used for IPv4 & IPv6 to avoid the recursive lookup problem?
use the exit interface to specify the next-hop address - useful for configuring static routes on point-to-point networks
What is a recursive lookup for IPv4 & IPv6?
when the router performs multiple lookups in the router table before forwarding a packet - it takes 2 lookups to forward a packet
What is a STUB network?
A network that is accessed by a single route, and the router has just 1 neighbor.
What system replaced classful addressing?
CIDR - increased addresses, reduced routing table size, created supernetting, reduces amount of bandwidth needed, and results in faster routing table lookups
List the AD for route sources:
Connected = 0 Static = 1 EIGRP = 90 OSPF = 110 RIP = 120
What is route resolvability?
In IPv4 & IPv6 - the routing table must determine the exit interface to use before the router forwards any packets
What is a default static route (IPv4 & IPv6)?
* a route that matches all packets * identifies gateway IP address to which the router sends all IP packets that it does not have a learned or static route to * 0.0.0.0/0 - destination IPv4 address * ::/0 destination IPv6 address * configuring a default static route creates a Gateway of Last Resort
What is the command to configure a default static route?
* can use ip-address of next-hop instead of exit interface
What are the 5 primary uses for static routing?
* easy routing table maintenance in small networks * routing to & from stub networks * creating a backup route * provide a Gateway of Last Resort for a stub network * connecting to a specific remote network - such as connecting a company's edge router to the ISP network
What is the command to configure a recursive (next-hop) static route?
* ip-address of next-hop
Which command can be used to verify a static route?
* show ip route static * an * in the routing table indicates it is selected as the Gateway of Last Resort
What are the 4 types of IPv4 & IPv6 static routes?
* standard * default * summary * floating
What is a supernet?
* summarizes multiple network addresses with a mask that is smaller than the classful mask * can be configured by static routes and classless routing protocols
When is a default static route typically used?
* when connecting an edge router to a service provider network * when connecting to a stub router
The next hop can be identified by an IP address, exit interface, or both. What are the 3 route types?
1. Next hop route - only next-hop IP address is specified 2. Directly connected static route - only the router exit interface is specified 3. Fully specified static route - both the next-hop IP address & exit interface are specified
The next hop IPv6 can be identified by an IPv6 address, exit interface, or both. What are the 3 route types?
1. Next hop static route - only next-hop IPv6 address is specified 2. Directly connected static route - only the router exit interface is specified 3. Fully specified static route - both the next-hop IPv6 address & exit interface are specified
Which is a valid summary route for networks 192.168.8.0/22, 192.168.12.0/22, and 192.168.16.0/22?
192.168.0.0/19
Refer to the exhibit - on R1 the command to configure a static route to network 172.16.2.0 by specifying the next-hop IP address is ip route 172.16.2.0 255.255.255.0
192.168.2.2
The G0/1 interface has a globally routable unicast address. What is used to create the interface ID portion of an IPv6 address?
EUI-64
In which situation in IPv6 must a fully specified static route be used?
if the IPv6 static route uses an IPv6 link-local address as the next-hop address - because IPv6 link-local addresses are not contained in the IPv6 routing table
What is FLSM?
Fixed-Length Subnet Masking - the same # of addresses are allocated for each subnet - wastes unused addresses
What commands, are used to determine if the configuration on router HQ works as designed? ip route 0.0.0.0 0.0.0.0 serial 0/0/0 10 ip route 0.0.0.0 0.0.0.0 serial 0/1/0
HQ(config)# interface serial 0/1/0 HQ(config-if)# shutdown HQ(config-if)# end HQ# show ip route
When CEF is enabled on the router, does a static route using a next-hop ID use recursive lookup?
NO, because CEF uses its FIB (which is a copy of the routing table) AND its adjacency table (which includes Layer 2 addressing) - so a static route only needs a single lookup with CEF
When is a fully specified static route used (IPv4 & IPv6)?
Older IOSs - prior to CEF or when CEF is disabled. When the exit interface is an Ethernet network, a fully specified static route is used including both the exit interface and the next-hop address.
Refer to the exhibit. Which set of commands will configure static routes that will allow the Park and the Alta routers to a) forward packets to each LAN and b) direct all other traffic to the Internet?
Park(config)# ip route 0.0.0.0 0.0.0.0 192.168.14.1 Alta(config)# ip route 10.0.234.0 255.255.255.0 192.168.14.2 Alta(config)# ip route 0.0.0.0 0.0.0.0 s0/0/0
To verify a specific entry in the routing table, use command:
R1# show ip route 192.168.2.1
To verify static routes, what command should be used?
R1# show ip route static | begin Gateway or R1# show running-config | section ip route
IPv6 show commands for troubleshooting?
R1# show ipv6 route R1# show ipv6 route static R1# show ipv6 route 2001:db8:acad:3:: show running-config | section ipv6 route
True or false - is it possible for a single static route to represent thousands of routes in a routing table?
TRUE
Unlike IPv4, IPv6 does not explicitly state that the default IPv6 is the Gateway of Last Resort. What is the key to making the default static IPv6 route match all packets?
The ::/0 mask indicates that none of the bits are required to match
Many networks combine dynamic routing protocols & static routes resulting in the router having multiple paths to the destination, so which path would it choose?
Static - has an AD of 1
How do you make a floating static route work?
configure it with a higher AD than the primary route - if there are multiple paths, the router chooses the path with the lowest AD
What kind of route is: ip route 0.0.0.0 0.0.0.0 S0/0/0?
default static route
Could the subnet mask 255.255.254.0 be used for a network that has a maximum of 300 devices?
Yes, it could be used for up to 510 devices.
If a route has a specific destination with a larger subnet mask and a default route, which one is used?
all routes with a specific destination take precedence over the default route
Why can't classful routing protocols send supernet routes?
because the receiving router automatically applies the default classful subnet mask to the network address in the routing table
Why should recursive lookups be avoided if possible?
because they consume router resources
The serial connection S0/0/0 is the DCE connection - which special configuration command does it require?
clock rate
Which commands are used to configure an IPv4 floating static route?
ip route 0.0.0.0 0.0.0.0 192.168.1.2 5 * the specified AD is 5, if you don't specify an AD #, it will default to 1
Which command is used to configure an IPv6 static route?
ipv6 route ::/0 2001:DB8:ACAD:4::2
To enable a router to forward IPv6 packets, what command must be configured?
ipv6 unicast-routing
How can you reduce the number of routing table entries?
multiple static entries can be summarized into 1 static route if destination networks are contiguous (and can be summarized into 1 single network address) and the multiple static routes all use the same exit interface or next-hop IP address
If you are using CEF, which kind of static route should you use?
next-hop address
When is a recursive static route valid for insertion into the routing table?
only when the specified next hop resolves to a valid exit interface
Common IOS troubleshooting commands:
ping traceroute show ip route show ip interface brief show cdp neighbors detail