OSPF TroubleShooting Note 

Troubleshooting OSPF Adjacencies

SHOW COMMAND TO VERIFY

• show ip ospf neighbor
• show ip packet
• show ip ospf database
• show ip ospf database router
• show ip ospf  database router self-originate
• show ip protocol
• show run | section ospf
• show ip protocols summary 
• show ip ospf border routes

OSPF Adjacency State Machine
  Normal OSPF Adjacency State Machine Order

• Down/Attempt
• Init ( one way hello - multicast is broken/layer2 issue)
• 2Way ( stop her for DRothers)
• ExStart ( MTU mistmatch/Duplicate router-ID, Pakcet loss. Access-list )
• Exchange
• Loading ( Neighbor sends bad packets or corrupt/ LS request ignored
• Full

Problem Indicator

• Init ( transport Issue / hello is sent but neighbor responded
• 2Way ( stop here from DRothers) ( Multicast/OSPF could be blocked)
•  Exstart ( First step of actual adjacency)
• Exchange ( Stub flags and other options happen here)
• Loading ( link state request packets are sent )
• Full 

Problem 

• Duplicate router id ( flood war)
• Attribute issues ( Broadcast/NBMA will us DR/BDR)