🔍 OSPF Neighbor Relationships and Troubleshooting in Palo Alto Networks

1. OSPF Neighbor States

OSPF neighbor relationships progress through several states before reaching full adjacency:

• Down: No Hello packets received.
• Init: Hello packet received, but the router's ID is not listed in the neighbor's Hello packet.
• 2-Way: Bidirectional communication established; routers see each other's ID in Hello packets.
• ExStart: Master-slave relationship established for database synchronization.
• Exchange: Database Description (DBD) packets exchanged.
• Loading: Link State Request (LSR) packets sent for missing LSAs.
• Full: Databases are fully synchronized; adjacency established.

For a detailed explanation, refer to the Palo Alto Networks documentation: OSPF Neighbors .

2. Designated Router (DR) and Backup Designated Router (BDR)

In multi-access networks (e.g., Ethernet), OSPF elects a DR and a BDR to reduce the number of adjacencies:

• DR: Primary router responsible for generating LSAs for the network.
• BDR: Takes over if the DR fails.
• DROTHER: Routers that are neither DR nor BDR; they form adjacencies only with DR and BDR.

Election is based on OSPF priority (0–255); higher values have higher priority. If priorities are equal, the router with the highest Router ID wins. A priority of 0 means the router is ineligible for DR/BDR election.

For configuration details, see: Network > Routing > Logical Routers > OSPF .

3. Troubleshooting OSPF Adjacency Issues

Common reasons for OSPF adjacency failures include:

• Mismatched OSPF parameters (e.g., Hello/Dead intervals, area ID, authentication).
• Layer 3 connectivity issues.
• MTU mismatches.
• Incorrect OSPF network types.

To troubleshoot, use the following CLI commands:

• show routing protocol ospf neighbor : Displays OSPF neighbor states.
• show routing protocol ospf interface : Shows OSPF-enabled interfaces and their settings.
• show routing protocol ospf lsdb : Displays the OSPF Link State Database.
• less mp-log routed.log : Views detailed OSPF logs.

For more information, refer to the knowledge base article: How to troubleshoot OSPF adjacency stuck in INIT or EXSTART or EXCHANGE or LOADING States .

4. Additional Resources

• Configure OSPF – Palo Alto Networks
• Confirm that OSPF Connections are Established
• OSPF Adjacencies are Established but the OSPF Routes are Not