Routing Protocol Troubleshooting

Troubleshooting steps when dealing with routing protocols

1. Verify connectivity between the two routers by pinging the other router.
– Show interfaces and show IP interfaces will list IP address information.
2. The routing protocol must pass authentication.
– For EIGRP: debug eigrp packets
– For OSPF: debug ospf adj | show ip ospf interface
3. For OSPF, the hello and dead timers must match.
– show ip ospf interface or show IP protocols.
4. Must use the same area for OSPF and ASN number for EIGRP.
– Show ip ospf interface brief | show IP eigrp interface | show ip protocols
5. OSPF router ID’s must be unique.

Reasons OSPFv2 won’t form a neighbourship

1. Interfaces must be in the same subnet.
2. Interfaces must both be up/up.
3. Neighbours must pass authentication.
4. Access-lists must not block OSPF.
5. Hello and dead timers must match.
6. Router ID’s must match.

Default Administrative Distances

Connected 0
Static 1
BGP(External) 20
EGRP 90
IGRP 100
OSPF 110
ISIS 115
RIP 120
EIGRP(External) 170
BGP(Internal) 200
Unusable 255