CCNA6-14

410 Chapter 6  IP Routing
11. What does RIPv2 use to prevent routing loops? (Choose two.)
A. CIDR
B. Split horizon
C. Authentication
D. Classless masking
E. Holddown timers
12. A network administrator views the output from the show ip route 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?
A. IGRP has a faster update timer.
B. IGRP has a lower administrative distance.
C. RIP has a higher metric value for that route.
D. The IGRP route has fewer hops.
E. The RIP path has a routing loop.
13. You type debug ip rip 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?
A. The route is 16 hops away.
B. The route has a delay of 16 microseconds.
C. The route is inaccessible.
D. The route is queued at 16 messages a second.
14. IGRP uses which of the following as default parameters for finding the best path to a remote
network? (Choose two.)
A. Hop count
B. MTU
C. Cumulative interface delay
D. STP
E. Path bandwidth value
15. 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?
Corp#sh ip route
[output cut]
R 192.168.215.0 [120/2] via 192.168.20.2, 00:00:23, Serial0/0
R 192.168.115.0 [120/1] via 192.168.20.2, 00:00:23, Serial0/0
R 192.168.30.0 [120/1] via 192.168.20.2, 00:00:23, Serial0/0
C 192.168.20.0 is directly connected, Serial0/0
C 192.168.214.0 is directly connected, FastEthernet0/0
Review Questions 411
A. The packet will be discarded.
B. The packet will be routed out the S0/0 interface.
C. The router will broadcast looking for the destination.
D. The packet will be routed out the Fa0/0 interface.
16. 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?
A. Any available route
B. RIP route
C. Static route
D. IGRP route
E. They will all load-balance.
17. You have the following routing table. Which of the following networks will not be placed in
the neighbor routing table?
R 192.168.30.0/24 [120/1] via 192.168.40.1, 00:00:12, Serial0
C 192.168.40.0/24 is directly connected, Serial0
172.16.0.0/24 is subnetted, 1 subnets
C 172.16.30.0 is directly connected, Loopback0
R 192.168.20.0/24 [120/1] via 192.168.40.1, 00:00:12, Serial0
R 10.0.0.0/8 [120/15] via 192.168.40.1, 00:00:07, Serial0
C 192.168.50.0/24 is directly connected, Ethernet0
A. 172.16.30.0
B. 192.168.30.0
C. 10.0.0.0
D. All of them will be placed in the neighbor routing table.
18. 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?
A. The updated information will be added to the existing routing table.
B. The update will be ignored and no further action will occur.
C. The updated information will replace the existing routing table entry.
D. The existing routing table entry will be deleted from the routing table and all routers will
exchange routing updates to reach convergence.
19. What is route poisoning?
A. It sends back the protocol received from a router as a poison pill, which stops the
regular updates.
B. It is information received from a router that can’t be sent back to the originating router.
C. It prevents regular update messages from reinstating a route that has just come up.
D. It describes when a router sets the metric for a downed link to infinity.
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20. Which of the following is true regarding RIPv2?
A. It has a lower administrative distance than RIPv1.
B. It converges faster than RIPv1.
C. It has the same timers as RIPv1.
D. It is harder to configure than RIPv1.
Answers to Review Questions 413
Answers to Review Questions
1. A, E. 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 answer 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 answer E with the ip default-network command.
2. C. The (config-router)#passive-interface command stops updates from being sent out
an interface, but route updates are still received.
3. A, B. 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.
4. C, F. The switches are not used as either a default gateway or other destination. Switches have
nothing to do with routing. It is very important to remember that the destination MAC address
will always be the router’s interface. The destination address of a frame, from HostA, will be
the MAC address of the F0/0 interface of RouterA. The destination address of a packet will
be the IP address of the network interface card (NIC) of the HTTPS server. The destination
port number in the segment header will have a value of 443 (HTTPS).
5. C, D. The route to 192.168.50.0 is unreachable and only interfaces s0/1 and FastEthernet
0/0 are participating in the RIP update. Since a route update was received, at least two routers
are participating in the RIP routing process. Since a route update for network 192.168.40.0 is
being sent out f0/0 and a route was received from 192.168.40.2, we can assume a ping to that
address will be successful.
6. A. A split horizon will not advertise a route back to the same router it learned the route from.
7. A, D. RouterC will use ICMP to inform HostA that HostB cannot be reached. It will perform
this by sending a destination unreachable ICMP message type.
8. B, E. 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.
9. B, C. 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.
10. B. Debug ip rip is used to show the Internet Protocol (IP) Routing Information Protocol
(RIP) updates being sent and received on the router.
11. B, E. 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. B. 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.
13. C. 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.
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14. C, E. 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.
15. A. 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.
16. C. 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.
17. C. 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.
18. B. 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.
19. D. 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).
20. C. RIPv2 is pretty much just like RIPv1. It has the same administrative distance and timers and
is configured just like RIPv1.
Answers to Written Lab 6 415
Answers to Written Lab 6
1. ip route 172.16.10.0 255.255.255.0 172.16.20.1
2. If the box next to an interface is unchecked, this means that passive-interface will not be
used and RIP will be sent and received on that interface.
3. ip route 0.0.0.0 0.0.0.0 172.16.40.1
4. Router(config)#ip classless
5. Stub network
6. Router#show ip route
7. Exit interface
8. False. The MAC address would be the router interface, not the remote host.
9. True
10. Router(config-if)#clock rate speed
11. Router rip, network 10.0.0.0
12. Router rip, passive-interface s1
13. Holddown timers
14. Route poisoning
15. Split horizon
16. debug ip rip