EIGRP GRE Troubleshooting Sim

Refer to the topology below. Your company asks you to identify the issues in Phase 1 EIGRP implementation. You have console access on R1, R2, R3 Branch1 and Branch2 routers. Only use show commands to troubleshoot the issues.

Question 1

Explanation

R1 routing table does not have any EIGRP learned routes so R1 or the link between R1 & R2 is the most likely problem. We should check if the IP addresses on R1 and R2 are correct or not with the “show ip interface brief” command.

Note: You should check the IP address of R2 E0/0 interface (the interface connected to R1) as well.

Question 2

Explanation

The “main office” here refers to R2 (and other routers behind it). Check Branch2 with the “show ip route” command:

We can see Branch2 only uses 192.168.12.1 (Branch 1 – the secondary path) to reach R2 and the subnets behind. Branch2 does not use the primary path (directly connected to R2) so there must be a problem with the connection between R2 and Branch2. Check Branch2 router with the “show running-config” command and we can see an access-list is blocking EIGRP packets advertised to Branch2.

Question 3

Explanation

This issue is same as Question 2 but this time it is R3 which causes the issue. We can check R3 with the “show running-config” command.

Question 4

Explanation

In this question we should check the local routers to see if these subnets have been advertised or not as there are many issues in the path which prevent these subnets from being shown in the routing tables.

When checking Branch1 router, we notice “network 172.16.0.0” is missing under EIGRP 200 so answer D is correct.