InterviewSolution

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This section includes InterviewSolutions, each offering curated multiple-choice questions to sharpen your knowledge and support exam preparation. Choose a topic below to get started.

1.	You type on your router console and see that 172.16.10.0 is being advertised to you with a metric of 16. What does this mean?
Answer» 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.

2.	The Corporate router receives an IP packet with a source IP address of 192.168.214.20 and a destination address of 192.168.22.3. Looking at the output from the Corporate router, what will the router do with this packet?
Answer» 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.

3.	If your routing table has a static, a RIP, and an IGRP route to the same network, which route will be used to route packets by default?
Answer» 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.

4.	What command is used to stop RIP routing updates from exiting out an interface but still allow the interface to receive RIP route updates?
Answer» The (config-router)#passive-interface command stops updates from being sent out an interface, but route updates are still received.

5.	Two connected routers are configured with RIP routing. What will be the result when a router receives a routing update that contains a higher-cost path to a network already in its routing table?
Answer» 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.

6.	Which command displays RIP routing updates?
Answer» 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.

7.	Which statement is true regarding classless routing protocols?
Answer» 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.

8.	What is split horizon?
Answer» A split horizon will not advertise a route back to the same router it learned the route from.

9.	What is route poisoning?
Answer» 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).

10.	A network administrator views the output from the command. A network that is advertised by both RIP and IGRP appears in the routing table flagged as an IGRP route. Why is the RIP route to this network not used in the routing table?
Answer» 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.

11.	What does RIPv2 use to prevent routing loops?
Answer» 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.

12.	Network 206.143.5.0 was assigned to the Acme Company to connect to its ISP. The administrator of Acme would like to configure one router with the commands to access the Internet. Which commands could be configured on the Gateway router to allow Internet access to the entire network?
Answer» 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.