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
IGRP 100
OSPF 110
ISIS 115
RIP 120
EIGRP(External) 170
BGP(Internal) 200
Unusable 255

About The Author

Timothy started his networking career in 2014, working for one of the largest telecommunication operators in Australia. He has a passion for networking and cyber security. When he's not working, he's obsessing over German Shepherd Dogs.