Mix Named/Classic EIGRP Redistribution troubleshooting: Infinity Feasible Distance, Wide Metric

Introduction

This tutorial covers the troubleshooting of route redistribution issues between Classic EIGRP and Named EIGRP. It focuses on the problem of missing routes due to high metric values caused by using the default redistribution seed metric. By following the steps outlined, you will learn how to configure your routers correctly, understand the significance of EIGRP metrics, and resolve the issues that arise when working with both EIGRP flavors.

Step 1: Set Up Your Network Environment

1. Connect Routers: Set up three routers (R1, R2, R3) as follows:
   • R1 (Named EIGRP)
   • R2 and R3 (Classic EIGRP)
2. Configure IP Addresses: Assign basic IP addresses:
   • R1:
     • Ethernet 0/0: 10.0.12.1/24
     • Loopback: 1.1.1.1/32
   • R2:
     • Ethernet 0/0: 10.0.12.2/24
     • Loopback: 2.2.2.2/32
     • Ethernet 0/1: 10.0.23.2/24
   • R3:
     • Ethernet 0/0: 10.0.23.3/24
     • Loopback: 3.3.3.3/32
3. Verify Connectivity: Use ping commands to ensure all interfaces are reachable.

Step 2: Configure Classic EIGRP on R2 and R3

1. Access Global Configuration Mode.
2. Configure EIGRP:
   • On R2:

     router eigrp 100
     no auto-summary
     network 10.0.23.0 0.0.0.3
     

   • On R3:

     router eigrp 100
     no auto-summary
     network 10.0.23.0 0.0.0.3
     

3. Redistribute Connected Interfaces: On both R2 and R3, redistribute the loopback interfaces:

   redistribute connected metric 1 1 1 1 1
   

4. Verify EIGRP Neighbors: Use the command show ip eigrp neighbors to confirm neighbor relationships.

Step 3: Configure Named EIGRP on R1

1. Access Global Configuration Mode.
2. Configure Named EIGRP:

   router eigrp 100
   address-family ipv4 unicast autonomous-system 100
   network 10.0.12.0
   

3. Verify Neighbors: Use show ip eigrp neighbors to ensure R1 sees R2 and R3 as neighbors.

Step 4: Identify Missing Routes

1. Check Routing Information:
   • On R1, run show ip route eigrp to see if routes from R2 and R3 appear.
   • You may notice routes are missing despite being visible in the EIGRP topology using show ip eigrp topology.

Step 5: Troubleshoot Metric Issues

1. Understand Metric Calculation:
   • Classic EIGRP uses a 32-bit metric calculation, while Named EIGRP uses a 64-bit calculation.
   • High metric values can cause routes to be seen as "infinity", preventing them from being installed in the routing table.
2. Verify Metrics: Check the feasible distance (FD) and advertised distance (AD) using:

   show ip eigrp topology
   

   Look for instances where FD is reported as infinity.

Step 6: Adjust Redistribution Metrics

1. Modify Seed Metrics: Change the redistribution command to use more realistic metrics. For example:

   redistribute connected metric 100000 1 255 1 1500
   

   • This sets a more appropriate bandwidth and other values.
2. Verify Changes: After adjusting the metrics, check if the routes appear in R1’s routing table.

Conclusion

By following these steps, you can successfully troubleshoot and resolve route redistribution issues between Classic and Named EIGRP. The key takeaway is to be mindful of the metrics used during redistribution and ensure they are set to values that can be accepted by the routing information base. If you continue to experience issues, consider revisiting your EIGRP configurations and metrics for further optimization.