Ip Routing MCQs with Explanations

Although answer D almost seems right, it is not; the mask is the mask used on the remote network, not the source network. Since there is no number at the end of the static route, it is using the default administrative distance of 1.

The debug ip rip command is used to show the Internet Protocol (IP) Routing Information Protocol (RIP) updates being sent and received on the router.

Classful routing means that all hosts in the internetwork use the same mask. Classless routing means that you can use Variable Length Subnet Masks (VLSMs) and can also support discontiguous networking.

The network 10.0.0.0 cannot be placed in the next router's routing table because it already is at 15 hops. One more hop would make the route 16 hops, and that is not valid in RIP networking.

A split horizon will not advertise a route back to the same router it learned the route from.

The (config-router) #passive-interface command stops updates from being sent out an interface, but route updates are still received.

When a routing update is received by a router, the router first checks the administrative distance (AD) and always chooses the route with the lowest AD. However, if two routes are received and they both have the same AD, then the router will choose the one route with the lowest metrics, or in RIP's case, hop count.

You cannot have 16 hops on a RIP network by default. If you receive a route advertised with a metric of 16, this means it is inaccessible.

Since the routing table shows no route to the 192.168.22.0 network, the router will discard the packet and send an ICMP destination unreachable message out interface FastEthernet 0/0, which is the source LAN where the packet originated from.

Static routes have an administrative distance of 1 by default. Unless you change this, a static route will always be used over any other found route. IGRP has an administrative distance of 100, and RIP has an administrative distance of 120, by default.

Another way to avoid problems caused by inconsistent updates and to stop network loops is route poisoning. When a network goes down, the distance-vector routing protocol initiates route poisoning by advertising the network with a metric of 16, or unreachable (sometimes referred to as infinite).

RIPv2 is pretty much just like RIPv1. It has the same administrative distance and timers and is configured just like RIPv1.

RIP has an administrative distance (AD) of 120, while IGRP has an administrative distance of 100, so the router will discard any route with a higher AD than 100.

RIPv2 uses the same timers and loop-avoidance schemes as RIPv1. Split horizon is used to stop an update from being sent out the same interface it was received on. Holddown timers allow time for a network to become stable in the case of a flapping link.

The distance-vector routing protocol sends its complete routing table out all active interfaces at periodic time intervals. Link-state routing protocols send updates containing the state of its own links to all routers in the internetwork.

IGRP uses bandwidth and delay of the line, by default, to determine the best path to a remote network. Delay of the line can sometimes be called the cumulative interface delay.

There are actually three different ways to configure the same default route, but only two are shown in the answer. First, you can set a default route with the 0.0.0.0 0.0.0.0 mask and then specify the next hop, as in option A. Or you can use 0.0.0.0 0.0.0.0 and use the exit interface instead of the next hop. Finally, you can use option D with the ip default-network command.