Troubleshooting Scenarios..

OSPF is stuck in ExStart. How would you troubleshoot it?

Answer:

  1. Check the OSPF neighbor state using show ip ospf neighbor.
  2. Verify that the MTU matches on both interfaces.
  3. Confirm unique Router IDs.
  4. Check OSPF authentication and network type.
  5. Review interface configuration and timers.
  6. Use debug ip ospf adj and, if needed, capture traffic with Wireshark ( type ospf in filter ) to inspect Hello and DBD packet exchanges and identify issues such as repeated DBD retransmissions or MTU mismatches.

Common Reasons OSPF Gets Stuck in ExStart

  • MTU mismatch (most common cause)
  • Duplicate Router ID
  • Network type mismatch
  • Interface misconfiguration
  • Authentication mismatch
  • Software bugs or hardware issues


What happens when you type google.com in a browser?

Expected answer:

  • DNS lookup
  • TCP handshake
  • HTTP/HTTPS request
  • Response from server


What will you do if a user cannot access a website?

Check:

  • Physical connectivity
  • IP configuration
  • Ping gateway
  • DNS resolution
  • Firewall

 A server is unreachable. How will you troubleshoot?

  1. Ping server
  2. Check IP
  3. Check gateway
  4. Verify routing
  5. Check firewall
  6. Check service status

Users report slow network performance. What will you check?

  • Bandwidth utilization
  • Packet loss
  • Interface errors
  • CPU utilization
  • Routing issues


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