Challenge: OSPF Neighbor Changing State from DOWN to DOWN

Here’s an interesting behavior I was able to create in a lab connecting two routers with a serial link:

*19:34:42.765: %OSPF-5-ADJCHG: Process 1, Nbr 10.0.1.1 on Serial1/0 from →
  EXSTART to DOWN, Neighbor Down: Too many retransmissions
*19:35:42.773: %OSPF-5-ADJCHG: Process 1, Nbr 10.0.1.1 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).

The challenge: what was going on and how was I able to produce these messages?

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10 comments:

  1. Masood Ahamd Shah 17 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. jumbo 17 November 2009 15:15
    Hay,

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

    -jumbo
  3. visir 17 November 2009 20:04
    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. Zeinovich 21 November 2009 21:43
    MTU mismatch prevent establishing adjacency
    sol
    1-(config)#system mtu routing "mtu_value"
    or
    2-(config-if)#ip ospf mtu ignore
    Zico
  5. Richard C Bedwell 18 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 xxx.xxx.xxx.xxx on VlanXXX from EXCHANGE to DOWN, Neighbor Down: Too many retransmissions
    %OSPF-5-ADJCHG: Process 1, Nbr xxx.xxx.xxx.xxx on VlanXXX from DOWN to DOWN, Neighbor Down: Ignore timer expired
  6. Ivan Pepelnjak 18 March 2011 16:36
    MTU mismatch ignored & oversized packet lost by one of the routers:

    http://blog.ioshints.info/2009/11/ip-ospf-mtu-ignore-is-dangerous-command.html
  7. Anonymous 01 April 2013 22:00
    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. Anonymous 17 June 2013 22:29
    you are using multicast, and multiaccesss environment, one of the routers keep sending prune message, which effect the ospf relation.
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