This section reviews troubleshooting for common routing protocols. A more theoretical explanation of the working of the protocols is available in the BSCI Quick Reference Guide.
Routers use three tables to make routing decisions: the routing table, ARP table, and CEF mappings
The routing table is visible using show ip route. Each entry in the routing table has an output interface or next hop. Packets are routed per the routing table, matching the longest prefix match first and then by other metrics determined by that IGP’s algorithm.
When a determination of the next hop has been made, the router needs to turn this information into a destination Layer 2 address. ...