Chapter 19 - Learning IPv4 Routes with RIPv2 Flashcards
Which of the following are features of RIPv2? (Choose two answers.)
a. Uses a hop-count metric
b. Sends update messages to broadcast address 255.255.255.255
c. After convergence, only sends updates if a change occurs
d. Uses split horizon as a loop prevention mechanism
A and D. RIPv2 includes many internal features, including using hop-count as the metric and split horizon as one of the loop prevention mechanisms. RIPv2 sends its updates to multicast address 224.0.0.9. It also sends periodic full routing updates all the time, even if the network is stable.
Which of the following best describes the concept of the RIP hop count metric?
a. The number of satellite links in a route.
b. The number of routers between a router and a subnet, not counting that router.
c. The number of routers between a router and a subnet, counting that router.
d. The number of links between a router and a subnet, not counting the link where the subnet resides.
e. The number of links between a router and a subnet, counting the link where the subnet resides.
B. The RIP hop-count metric refers to routers as hops. (That fact rules out three of the answers.) From the perspective of a router that has a RIP route, the hop count includes 1 for each router between the local router and the destination subnet, but does not include 1 for the router itself. For instance, imagine a route on R1 for some subnet, and that route has a metric 2. That could occur if the end-to-end path from R1 to that subnet ran from R1, through R2, then through R3, and then on to the link where the subnet resides.
Router R2 has interfaces with addresses/masks of 10.1.1.2/24 and 11.1.1.2/24. Which of the following commands would be part of a RIP Version 2 configuration on R2 that enables RIPv2 on both interfaces? (Choose three answers.)
a. router rip
b. router rip 3
c. network 10.0.0.0
d. network 10.1.1.1
e. network 11.0.0.0
f. network 11.1.1.2
A, C, and E. The RIPv2 network commands refer to the classful network (the Class A, B, or C) network in which an interface address resides, rather than the subnet number or interface address. So, the two network commands that refer to Class A networks 10.0.0.0 and 11.0.0.0 are correct. Also, RIP uses the router rip global command, with no other parameter, to move the user into RIP configuration mode so that the network commands can be configured.
Which of the following network commands, following a router rip command, would cause RIP to send updates out two interfaces whose IP addresses are 10.1.2.1 and 10.1.1.1, mask 255.255.255.0?
a. network 10.0.0.0
b. network 10.1.1.0 10.1.2.0
c. network 10.1.1.1. 10.1.2.1
d. network 10.1.0.0 255.255.0.0
e. network 10
A. The RIPv2 network commands refer to the classful network (the Class A, B, or C) network in which an interface address resides, rather than the subnet number or interface address. The network 10.0.0.0 command enables RIP on all interfaces on the local router that happen to have addresses in network 10.0.0.0.
Review the snippet from a show ip route command on a router:
R 10.1.2.0 [120/1] via 10.1.128.252, 00:00:13,
Serial0/0/1
Which of the following statements must be true regarding this output? (Choose two answers.)
a. The administrative distance is 1.
b. The administrative distance is 120.
c. The metric is 1.
d. The metric is not listed.
e. The router added this route to the routing table 13 seconds ago.
f. The router must wait 13 seconds before advertising this route again.
B and C. The answers refer to several numbers listed in the line of output. The two numbers in brackets, 120 and 1, refer to the administrative distance (120) and the metric (1). The reference to 13 seconds, per the counter of 00:00:13, refers to the counter that shows how long it has been since this router last heard about this route from the neighboring RIP router. However, the route may have been added a much longer time ago; the timer shows how long since the most recent update, not how long since the route was first added to the local router’s routing table.
Review the snippet from a show ip protocols command on a router:
Automatic network summarization is not in effect Maximum path: 5 Routing for Networks: 192.168.1.0 192.168.5.0 Passive Interface(s): GigabitEthernet0/1
Which of the following commands would you expect the show running-config command to list in RIP configuration mode? (Choose two answers.)
a. auto-summary
b. network 192.168.5.1
c. maximum-paths 5
d. passive-interface gigabitethernet0/1
C and D. The output reveals the following configuration: router rip, maximum-paths 5, passive-interface gigabitethernet0/1, network 192.168.1.0, network 192.168.5.0, and no auto-summary.
Routers R1 and R2 use RIPv2, and should exchange routes with each other. R1 and R2 connect on an Ethernet link, with both routers using their G0/0 interfaces. R2 learns routes from R1, but R1 does not learn routes from R2. Which of the following mistakes could result in this symptom?
a. R2 has configured a passive-interface gigabitethernet0/0 command.
b. R1’s and R2’s IP address/mask values are 10.1.1.1/25 and 10.1.1.201/25, respectively.
c. R1’s has no RIP network command that matches R1’s G0/0 interface IP address.
d. R2 is missing a no auto-summary command.
A. Of the four answers, the one incorrect answer is the one case in which routing information is exchanged in one direction only. In this case, R2, as a passive router, does not advertise to R1, so R1 does not learn routes. R2 still learns routes.
Two wrong answers mention problems that would stop both routers from learning routes from each other. The answer that lists IP addresses that are in different subnets causes both routers to ignore each other’s RIP updates. The answer about R1’s missing network command means that R1 would neither send nor process any received updates on its G0/0 interface, so neither R1 nor R2 would learn from each other. Finally, the answer that mentions the no auto-summary command would not prevent a router from learning routes; it would only change what routes a router would advertise.
