Week 5 Discussion Open Shortest Path First OSPF and EIGRP

Week 5 Discussion: “Open Shortest Path First (OSPF) and EIGRP Please respond to the following:

Suggest the troubleshooting preparations that you believe are necessary to diagnose and resolve problems related to EIGRP. Suggest what you believe to be the most effective and the least effective tool(s) available to both monitor and debug EIGRP. Provide a rationale for your response.

Imagine that you have been tasked with gathering information from the OSPF data structures, observing the transmission and reception of packets, and observing the exchange of routing information. Suggest the commands that you would use to accomplish these tasks and explain the strategies that you would employ to ensure that these commands do not affect router performance. Provide a rationale for your response.


After configuring EIGRP, we first test connectivity to the remote network, using ping. If the ping fails, check that the router has EIGRP neighbors and troubleshoot on a link-by-link basis. Neighbor adjacency might not be running for a number of reasons. EIGRP is an advanced distance vector routing protocol that has to establish a neighbor relationship before updates are sent; therefore, we next check if the neighbor adjacency is working properly. If so, we can continue by checking if networks are being advertised or not. Issues that affect EIGRP neighbor adjacencies are uncommon subnets, K value mismatches, AS mismatches, layer 2 issues, access-list issues and NBMA (Non Broadcast Multi Access). Uncommon subnets are EIGRP neighbors with IP addresses that are not in the same subnet. By default bandwidth and delay are enabled for the metric calculation. We can enable load and reliability but we have to do it on all EIGRP routers to prevent AS mismatch: The autonomous system number has to match on both EIGRP routers in order to form a neighbor adjacency to avoid K value mismatches. EIGRP works on layer 3 of the OSI-model. If layer 1 and 2 are not working properly we’ll have issues with forming a neighbor adjacency that creates layer 2 issues. Access-list issues arise from the possibility that someone created an access-list that filters out multicast traffic. EIGRP by default uses to communicate with other EIGRP neighbors. NBMA networks like frame-relay will not allow broadcast or multicast traffic by default. This can prevent EIGRP from forming EIGRP neighbor adjacencies. The debug eigrp commands are the best tools to used to troubleshoot or monitor live EIGRP processes.

There are many debug commands effective against troubleshooting EIGRP. You can use the debug eigrp packets command to troubleshoot when hello packet information does not match. The debug ip routing command output verifies whether a route is being installed. This debug shows all the routes that the routing table takes out and installs, although the output of the debug might be overwhelming to the routers. You can also use an access list to the debug so that the output shows only the routes in question.

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