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Challenge: OSPF neighbor changing state from DOWN to DOWN

I’ve had an interesting discussion with Nicolas who optimized my OSPF neighbor loss EEM applet assuming the OSPF-5-ADJCHG message reports only OSPF neighbor state transitions from DOWN to FULL and from FULL to DOWN. I knew I'd seen stranger messages in my lab and was able to produce these ones after fumbling with OSPF configurations of two routers connected with a serial link:

*19:34:42.765: %OSPF-5-ADJCHG: Process 1, Nbr on Serial1/0 from →
  EXSTART to DOWN, Neighbor Down: Too many retransmissions
*19:35:42.773: %OSPF-5-ADJCHG: Process 1, Nbr on Serial1/0 from →
  DOWN to DOWN, Neighbor Down: Ignore timer expired

The messages are repeated approximately every three minutes (using the default OSPF timers).

Here's the challenge: what was going on and how was I able to produce these messages?

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  1. Masood Ahamd Shah17 November, 2009 08:41

    dbd packets are being filtered/dropped for some reason such as:

    mtu mismatch.
    access-list if you block unicast OSPF between the boxes you'll get exactly the symptoms ...

  2. Hay,

    Too many retransmissions - buggy line
    Neighbor Down: Ignore timer expired - ospf message-digest-key is configured only one side


  3. There is hidden "ignore" timer. If neighbor do something wrong its ignored for period of that timer.
    How too reproduce this: on one of two routers connected by Ethernet interfaces filter unicast (but not multicast) packets of ospf protocol in both directions - routers will periodically establish two-way adjacency, but they can't exchange their databases...

  4. MTU mismatch prevent establishing adjacency
    1-(config)#system mtu routing "mtu_value"
    2-(config-if)#ip ospf mtu ignore

  5. Richard C Bedwell18 March, 2011 13:58

    I don't know how you did it, but I'm trying to work an OSPF relationship between a Juniper and a Cisco Router, and I keep getting the following

    %OSPF-5-ADJCHG: Process 1, Nbr on VlanXXX from EXCHANGE to DOWN, Neighbor Down: Too many retransmissions
    %OSPF-5-ADJCHG: Process 1, Nbr on VlanXXX from DOWN to DOWN, Neighbor Down: Ignore timer expired

  6. Ivan Pepelnjak18 March, 2011 16:36

    MTU mismatch ignored & oversized packet lost by one of the routers:

  7. I get the same message even though the MTUs on both sides are the same. What more can be wrong, if the MTU missmatch is not the case???

  8. you are using multicast, and multiaccesss environment, one of the routers keep sending prune message, which effect the ospf relation.


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