1. Address families: Verify that the correct address families (IPv4 or IPv6) are being used in the EIGRP configuration. Check the EIGRP configuration to ensure that the correct network statements are present for the intended address family.
2. Neighbor relationship and authentication:
Verify that EIGRP neighbor relationships are established between routers. Check for errors in the neighbor configuration, and verify that authentication is enabled and configured correctly.
3. Loop-free path selection: Verify that EIGRP is selecting loop-free paths to destination networks. Check the EIGRP topology table for the path selection metrics (RD, FD, FC, successor, feasible successor, stuck in active) and verify that the expected paths are selected.
4. Stubs: Verify that EIGRP stubs are configured correctly. Check the stub configuration to ensure that the correct networks are being stubbed, and that the stub router is able to receive EIGRP updates from its neighbors.
5. Load balancing: Verify that EIGRP load balancing is configured correctly. Check the load balancing configuration to ensure that it is set to either equal or unequal cost, as desired. Verify that the correct load balancing paths are being selected.
6. Metrics: Verify that EIGRP metrics are configured correctly. Check the metric configuration to ensure that it is set to the desired values for the network.
7. Use debug commands to troubleshoot EIGRP issues. Debugging can provide valuable information about EIGRP behavior and can help to identify configuration errors or network connectivity problems.
By following these troubleshooting steps, you can identify and resolve issues with EIGRP in both classic and named mode.
1.10 Troubleshoot OSPF (v2/v3)
OSPF (Open Shortest Path First) is a link-state routing protocol used to route IP traffic within a network. Here are the steps to troubleshoot OSPF:
1. Address families: Verify that the correct address families (IPv4 or IPv6) are being used in the OSPF configuration. Check the OSPF configuration to ensure that the correct network statements are present for the intended address family.
2. Neighbor relationship and authentication: Verify that OSPF neighbor relationships are established between routers. Check for errors in the neighbor configuration, and verify that authentication is enabled and configured correctly.
3. Network types, area types, and router types: Verify that OSPF network types, area types, and router types are configured correctly. Check for errors in the OSPF configuration, and verify that the correct network types, area types, and router types are being used.
4. Path preference: Verify that OSPF is selecting the correct paths to destination networks. Check the OSPF topology table for the path selection metrics and verify that the expected paths are selected.
5. Use debug commands to troubleshoot OSPF issues. Debugging can provide valuable information about OSPF behavior and can help to identify configuration errors or network connectivity problems.
By following these troubleshooting steps, you can identify and resolve issues with OSPF in both v2 and v3 versions. Additionally, you can troubleshoot specific aspects of OSPF, such as neighbor relationships, network types, area types, router types, and path preference.
1.11 Troubleshoot BGP (Internal and External)
1.11.a Address families (IPv4, IPv6)
BGP (Border Gateway Protocol) is an inter-domain routing protocol used to exchange routing information between different autonomous systems (AS). Here are the steps to troubleshoot BGP:
1. Address families: Verify that the correct address families (IPv4 or IPv6) are being used in the BGP configuration. Check the BGP configuration to ensure that the correct network statements are present for the intended address family.
2. Verify BGP neighbor relationships: Verify that BGP neighbor relationships are established between routers. Check for errors in the neighbor configuration, and verify that authentication is enabled and configured correctly.
3. Verify BGP path selection: Verify that BGP is selecting the correct paths to destination networks. Check the BGP table for the path selection metrics and verify that the expected paths are selected.
4. Verify BGP peering status: Check the peering status of BGP sessions to verify that they are up and running.
5. Verify BGP routing information: Check BGP routes and routing tables to ensure that they contain the correct information and are properly advertised.
6. Check for BGP-related errors: Check the log files for any BGP-related errors or warnings that may provide clues to the source of the problem.
7. Use debug commands to troubleshoot BGP issues. Debugging can provide valuable information about BGP behavior and can help to identify configuration errors or network connectivity problems.
By following these troubleshooting steps, you can identify and resolve issues with BGP in both internal and external contexts. Additionally, you can troubleshoot specific aspects of BGP, such as address families, neighbor relationships, path selection, peering status, routing information, and errors.
1.11.b Neighbor relationship and authentication (next-hop, mulithop, 4-byte AS, private AS, route refresh, synchronization, operation, peer group, states and timers)
In addition to the address families mentioned in 1.11.a, troubleshooting BGP neighbor relationships and authentication involves verifying the following:
1. Next-hop: Verify that the next-hop attribute is correct for each BGP route. If the next-hop is not reachable, BGP will not install the route in the routing table.
2. Multihop: Verify that BGP is configured to use multihop if the neighbor is not directly connected. Check that the BGP peering is configured with the correct IP addresses and the right number of hops.
3. 4-byte AS and private AS: Verify that BGP is configured to support 4-byte AS numbers and private AS numbers, if necessary.
4. Route refresh: Verify that the BGP configuration includes route refresh support, which enables BGP peers to exchange updates without resetting the entire BGP session.
5. Synchronization: Verify that BGP synchronization is disabled or enabled as required. BGP synchronization ensures that the BGP routing table reflects the IGP (Interior Gateway Protocol) routing table, and is typically used in scenarios where the network has a mix of BGP and IGP routing.
6. Operation: Verify that the BGP configuration is correct, and that the correct BGP protocol is used (iBGP or eBGP).
7. Peer group: Verify that the BGP configuration includes the correct peer group settings, if used.
8. States and timers: Verify the BGP peering states and timers to ensure that the BGP sessions are functioning correctly. Check for errors in the BGP configuration and verify that the correct timers are set.
By following these troubleshooting steps, you can identify and resolve issues with BGP neighbor relationships and authentication. Additionally, you can troubleshoot specific aspects of BGP, such as next-hop, multihop, 4-byte AS and private AS, route refresh, synchronization, operation, peer group, states, and timers.
