EIGRP Troubleshooting

Troubleshooting EIGRP issues often involves verifying neighbor relationships, checking routing tables, and examining interface configurations. Here are some common issues and troubleshooting steps:

Common EIGRP Issues:

  • Neighbor Adjacency Issues: EIGRP neighbors may not form an adjacency due to mismatched AS numbers, authentication issues, K-value mismatches, or ACLs blocking EIGRP packets.
  • Missing Routes: Routes may not be advertised or learned due to incorrect network statements, passive interfaces, or summarization issues.
  • Stuck in Active (SIA): A router may get stuck in active state if it sends a query and does not receive a reply from a neighbor within a certain time. This can indicate a problem with the neighbor or a link failure.

Troubleshooting Steps:

  1. Verify EIGRP Neighbors: Use show ip eigrp neighbors to check if neighbors are established. Look for the correct AS number and hold time.
  2. Check EIGRP Interfaces: Use show ip eigrp interfaces detail to verify that EIGRP is enabled on the correct interfaces and that there are no passive interface issues.
  3. Examine EIGRP Topology Table: Use show ip eigrp topology to see learned routes, feasible successors, and reported distances.
  4. Check Routing Table: Use show ip route eigrp to confirm that EIGRP routes are being installed in the routing table.
  5. Debug EIGRP Packets: Use debug eigrp packets (use with caution in production) to see EIGRP packets being sent and received, which can help identify communication issues.
  6. Verify K-values: Ensure K-values are consistent across all EIGRP routers in the same AS. Use show ip protocols.
  7. Check Authentication: If authentication is configured, verify that key chains and authentication modes match on neighboring routers.