CCNA Questions/Answers Routing Protocols

Transcription

1 Refer to the exhibit and configuration shown above. Routers R1 and R2 are properly configured with eigrp 976 protocol and are able to ping interfaces fa0/1 and fa0/2, respectively. Which commands are necessary to be added on R3, communication to be done between routers? A. R3(config)#router rip R3(config-router)#network area 0 B. R3(config)#router eigrp 976 R3(config-router)#network C. R3(config)#router eigrp area 0 R3(config-router)#netwrok D. R3(config)#router eigrp 976 R3(config-router)#netwrok Answer: B EIGRP protocol with autonomous system number 976 is used to configure devices on address space /26 (from to ). In this case Host3 will be able to communicate through R3 router. More on: Link

2 You want to set up company network, with one Cisco 2811 router, two Cisco switches and maximum of 32 hosts. Routing updates should be keep to minimum. Which routing protocol is most appropriate for this? A. IGRP B. EIGRP C. RIPv2 D. BGP E. RIPv1 Answer: B For this scenario it is necessary dynamic environment, with limited number of IP addresses, with VLSM (Variable Length Subnet Masking) employed, so routing protocol should be classless. EIGRP is hybrid routing protocol that is classless and very efficient in term of network resources. EIGRP is Cisco proprietary protocol, so all devices in the network must be Cisco devices. RIPv1 and IGRP are clasfull protocols and don t support VLSM. BGP is typically used for exchange routing information between autonomous systems (between company and ISP, or between ISPs). RIPv2 supports VLSM, but is limited to hop counts of 15 and uses more bandwidth than EIGRP (because periodically broadcasts routing information). More on: Link

3 Information provided for network topology is: R1: OSPF priority 128; fa0/ ; fa0/ ; fa0/ ; fa0/ ; fa0/ ; R2: OSPF priority 1; fa0/ ; fa0/ ; loopback ; R3: OSPF priority 10; fa0/ ; fa0/ ; fa0/ ; R4: OSPF priority 128; fa0/ ; fa0/ ; R5: OSPF priority 1; fa0/ ; fa0/ ; loopback ; Which router will be DR (Designated Router) if network is configured within OSPF area 1? A. R1 B. R2 C. R3 D. R4 E. R5 Answer: A By default, all Cisco IOS OSPF routers are assigned a router priority of 1 (can be in value from 0 to 255). A priority of 0 is used to prevent a router from ever becoming DR

4 We can influence the DR election process by administratively configuring higher priorities for routers we want to win the DR election. Suppose we wanted R5 to become the DR we can put highest priority than other routers (R1 to R4): R5(config)# interface f0/1 R5(config-if)# ip ospf priority 255 DR is router that got highest OSPF priority. Router with lower priority than DR becomes BDR. If there are more routers with the same OSPF priority, then DR is router that got highest loopback address. If loopback addresses are not configured on routers that got same OSPF priority, then router with highest IP address from configured interfaces will become DR. In our case R1 and R4 got same OSPF priority. R1 will become DR because got highest IP address configured on its interfaces. R4 will be elected as BDR. More on: Link

5 You use Telnet session to gain into RouterA from your PC. Main reason for this is to check if there are RIP updates on the router. You use command RouterA#debug ip rip and you haven t received any output from it. What is the reason for this? (Choose two) A. RouterA is configurured with EIGRP, not with RIP. B. RIP version is version 2. C. Command should be in a form: RouterA(config)#debug ip rip D. You have to issue RouterA#terminal monitor on router. E. OSPF and EIGRP can be debugged; but Cisco routers don t support RIP debugging. Answer: A, D This command allows you to see the console output of a router that you are connected with Telnet to. RouterA#terminal monitor In this example, we don't see any output from the debug ip rip command until the terminal monitor command is entered. If router is not configured with RIP it is obvious that debug ip rip command will have nothing on the output

6 Refer to the exhibit. RouterB is DCE device and is configured properly with RIPv2. Configure RouterA with RIPv2, PC1 to be able to send traffic to the PC2. What are the proper commands to do this? A. RouterA(config)#int fa0/0 RouterA(config-if)#ip address RouterA(config)#int s0/0 RouterA(config-if)#ip address RouterA(config-if)#exit RouterA(config)#router rip RouterA(config-router)#version 2 RouterA(config-router)#network RouterA(config-router)# network B. RouterA(config)#int fa0/0 RouterA(config-if)#ip address RouterA(config)#int s0/0 RouterA(config-if)#ip address RouterA(config-if)#exit

7 RouterA(config)#router rip RouterA(config-router)#version 2 RouterA(config-router)#network RouterA(config-router)# network C. RouterA(config)#int fa0/0 RouterA(config-if)#ip address RouterA(config)#int s0/0 RouterA(config-if)#ip address RouterA(config-if)#exit RouterA(config)#router rip RouterA(config-router)#version 2 RouterA(config-router)#network RouterA(config-router)# network D. RouterA(config)#int fa0/0 RouterA(config-if)#ip address RouterA(config)#int s0/0 RouterA(config-if)#ip address RouterA(config-if)#exit RouterA(config)#router rip RouterA(config-router)#network RouterA(config-router)# network Answer: A On RouterA you have to configure interfaces fa0/0 and s0/0 with IP addresses and to configure RIPv2 protocol

8 To configure RIPv2 you have to use following command: RouterA(config-router)#version 2 More on: Link

9 You are configuring default RIP protocol settings on a router. What statement is true? A. Router will send RIPv1 updates. B. Router will send RIPv2 updates. C. Router will send RIPv1 and RIPv2 updates. D. Router will send RIPv1 and RIPv2 updates and receive RIPv1 and RIPv2 updates. E. Router will send RIPv1 updates and receive RIPv1 and RIPv2 updates. F. Router will send RIPv2 updates and receive RIPv1 and RIPv2 updates. Answer: E By default router is configured with RIP version 1. To change to version 2 you have to add command: Router(config)#router rip Router(config-router)#version 2 By default, RIPv1 will accept RIPv1 and RIPv2 updates. However, RIP v2 will not accept RIPv1 updates. So, solve this problem RIPv2 must be configured to accept RIPv1 updates with commands: R1(config-if)#interface serial 0/0 R1(config-if)#ip rip receive version

10 Refer to the exhibit and given show commands. What output of the RouterA#show ip route command is correct? A. R [120/1] via , 00:00:08, Serial0/0 B. R [120/1] via , 00:00:08, Serial0/0 C. R [90/1] via , 00:00:08, Serial0/0 D. C /24 is directly connected, FastEthernet0/0 E. C /24 is directly connected, Serial0/0 Answer: B, D Let see what the meaning of the first output is: R [120/1] via , 00:00:08, Serial0/

11 R - at the beginning of statement from show ip route command output indicates that this is RIP route gives destination network for this route ( /24). [120/1] gives that administrative distance is 120 and metric is 1 for the route (RIP got administrative distance of 120). via gives next hop IP address of interface s0/0 on RouterB. 00:00:08 gives time when route was updated before. Serial0/0 is output interface on RouterA. Let see what the meaning of the second output is: C /24 is directly connected, FastEthernet0/0 C at the beginning of statement from show ip route command output indicates that this is directly connected route to one of the present router interfaces (in this case interface FastEthernet0/0). More on: Link

12 Which routing protocol divides autonomous system into areas? A. RIP B. EIGRP C. IGRP D. OSPF Answer: D OSPF is link state protocol that divides autonomous system into areas. This is useful for situation where routing updates have to be limited to the particular part of the network. Areas are introduced to put a boundary on the explosion of link-state updates. Flooding and calculation of the Dijkstra algorithm on a router is limited to changes within an area. All routers within an area have the exact link-state database. Routers that belong to multiple areas, and connect these areas to the backbone area are called area border routers (ABR). ABRs must therefore maintain information describing the backbone areas and other attached areas. An area is interface specific. A router that has all of its interfaces within the same area is called an internal router (IR). A router that has interfaces in multiple areas is called an area border router (ABR). Routers that act as gateways (redistribution) between OSPF and other routing protocols (IGRP, EIGRP, IS-IS, RIP, BGP, Static) or other instances of the OSPF routing process are called autonomous system boundary router (ASBR). Any router can be an ABR or an ASBR. More on: Link