CISCO CCNA 200-301 Q26

You have three EIGRP routers that are connected as shown in the diagram below.

Router A and Router C do not seem to be exchanging information. You execute commands on all three routers, and receive as output the information shown below:

What needs to be done to make Routers A and C start exchanging information?

A. Execute the auto-summary command on Router A
B. Correct the IP address on the S1 interface of Router C
C. Recreate the EIGRP configuration on Router C as EIGRP 55
D. Execute the network command under EIGRP 56 on Router C

Correct Answers: D

Router C is not displayed in the neighbor table of Router A, which indicates that Router C and Router A are not forming a neighbor relationship or exchanging information. This is because Router C does not have EIGRP configured for its S1 interface. You can see this is missing from its configuration in the output of the show run command for RouterC. To solve the issue, you should execute the network command under the EIGRP 56 configuration on Router C. Then Router C will start sending hellos on that interface and the two routers will become neighbors.

The show ip eigrp neighbors command displays the following information for each EIGRP neighbor. In parentheses is the value of each found in the output of router A for Router B:

IP address (
Local interface (S1)
Retransmit interval (13)
Queue count (100)

There is no need to execute the auto-summary command on Router A. It will not affect the establishment of a neighbor relationship between Routers A and C.

There is no need to correct the IP address on the S1 interface of Router C. The address is correctly located in the same subnet as the address on S0 of Router A.

Finally, changing the EIGRP configuration on Router C to EIGRP 55 will not help. Router C will not start sending hellos on its S1 interface until EIGRP is enabled on the S1 interface. Until then, the Routers A and C will not form a neighbor relationship and will not share information.