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OSPF between 6880X and 3560 started flapping

Hello!

 

We have got a 6880X and a 3560 with two fibre links between them (running different OSPF's, each link has 3 different OSPF networks).

 

6880X { vlan 3112,3312,3512 } 3560
      { vlan 3113,3313,3513 }

The thing is that one of these links has started acting up lately, with all three OSPF networks (vlan 3112,3312,3512) timing out (although not necesserily at the same time):

%OSPF-SW1-5-ADJCHG: Process 2, Nbr 20.60.60.60 on Vlan3112 from FULL to DOWN, Neighbor Down: Dead timer expired

 

While looking at the OSPF timers, I see that they sometimes get way below 30 seconds (which should be the minimum value we'd see in normal conditions), before popping back up to 40 (standard 40/10 timers).

But sometimes it reaches 0 and the link drops.

 

Layer 2 connectivity (ping that is) between switches seems to be ok at all times.

 

I've looked config backups from before the problems started, but can't find anything relevant that's different.

 

I'm by no means an OSPF expert, so any help is greatly appreciated.

Oh, by the way, the links between the switches are QinQ's which we rent from another ISP, but they of course claim everything on their side is ship shape.

 

A snip of "debug ip ospf adj"

(i see a strange "ignored due to unknown neighbor"message here, at 11:35:12.360:

*Jan 12 11:33:32.380: SW1: OSPF-2 ADJ   Vl3112: Nbr 20.60.60.60: Clean-up dbase exchange
*Jan 12 11:34:16.704: SW1: OSPF-2 ADJ   Vl3112: 20.60.60.60 address 10.1.1.225 is dead
*Jan 12 11:34:16.704: SW1: OSPF-2 ADJ   Vl3112: 20.60.60.60 address 10.1.1.225 is dead, state DOWN
*Jan 12 11:34:16.704: %OSPF-SW1-5-ADJCHG: Process 2, Nbr 20.60.60.60 on Vlan3112 from FULL to DOWN, Neighbor Down: Dead timer expired
*Jan 12 11:34:16.704: SW1: OSPF-2 ADJ   Vl3112: Neighbor change event
*Jan 12 11:34:16.704: SW1: OSPF-2 ADJ   Vl3112: DR/BDR election
*Jan 12 11:34:16.704: SW1: OSPF-2 ADJ   Vl3112: Elect BDR 2.7.7.7
*Jan 12 11:34:16.704: SW1: OSPF-2 ADJ   Vl3112: Elect DR 2.7.7.7
*Jan 12 11:34:16.704: SW1: OSPF-2 ADJ   Vl3112: Elect BDR 0.0.0.0
*Jan 12 11:34:16.704: SW1: OSPF-2 ADJ   Vl3112: Elect DR 2.7.7.7
*Jan 12 11:34:16.704: SW1: OSPF-2 ADJ   Vl3112: DR: 2.7.7.7 (Id)
*Jan 12 11:34:16.704: SW1: OSPF-2 ADJ   Vl3112:    BDR: none
*Jan 12 11:34:16.704: SW1: OSPF-2 ADJ   Vl3112: Reset flush timer
*Jan 12 11:34:16.704: SW1: OSPF-2 ADJ   Vl3112: Remember old DR 20.60.60.60 (id)
*Jan 12 11:34:17.724: SW1: OSPF-2 ADJ   Vl3112: 2 Way Communication to 20.60.60.60, state 2WAY
*Jan 12 11:34:17.724: SW1: OSPF-2 ADJ   Vl3112: Neighbor change event
*Jan 12 11:34:17.724: SW1: OSPF-2 ADJ   Vl3112: DR/BDR election
*Jan 12 11:34:17.724: SW1: OSPF-2 ADJ   Vl3112: Elect BDR 0.0.0.0
*Jan 12 11:34:17.724: SW1: OSPF-2 ADJ   Vl3112: Elect DR 20.60.60.60
*Jan 12 11:34:17.724: SW1: OSPF-2 ADJ   Vl3112: Elect BDR 2.7.7.7
*Jan 12 11:34:17.724: SW1: OSPF-2 ADJ   Vl3112: Elect DR 20.60.60.60
*Jan 12 11:34:17.724: SW1: OSPF-2 ADJ   Vl3112: DR: 20.60.60.60 (Id)
*Jan 12 11:34:17.724: SW1: OSPF-2 ADJ   Vl3112:    BDR: 2.7.7.7 (Id)
*Jan 12 11:34:17.724: SW1: OSPF-2 ADJ   Vl3112: Nbr 20.60.60.60: Prepare dbase exchange
*Jan 12 11:34:17.724: SW1: OSPF-2 ADJ   Vl3112: Send DBD to 20.60.60.60 seq 0x237B opt 0x52 flag 0x7 len 32
*Jan 12 11:34:17.724: SW1: OSPF-2 ADJ   Vl3112: Set flush timer
*Jan 12 11:34:17.724: SW1: OSPF-2 ADJ   Vl3112: Remember old DR 2.7.7.7 (id)
*Jan 12 11:34:17.724: SW1: OSPF-2 ADJ   Vl3112: Neighbor change event
*Jan 12 11:34:17.724: SW1: OSPF-2 ADJ   Vl3112: DR/BDR election
*Jan 12 11:34:17.724: SW1: OSPF-2 ADJ   Vl3112: Elect BDR 2.7.7.7
*Jan 12 11:34:17.724: SW1: OSPF-2 ADJ   Vl3112: Elect DR 20.60.60.60
*Jan 12 11:34:17.724: SW1: OSPF-2 ADJ   Vl3112: DR: 20.60.60.60 (Id)
*Jan 12 11:34:17.724: SW1: OSPF-2 ADJ   Vl3112:    BDR: 2.7.7.7 (Id)
*Jan 12 11:34:17.732: SW1: OSPF-2 ADJ   Vl3112: Rcv DBD from 20.60.60.60 seq 0x6A7E opt 0x52 flag 0x7 len 32  mtu 1500 state EXSTART
*Jan 12 11:34:17.732: SW1: OSPF-2 ADJ   Vl3112: NBR Negotiation Done. We are the SLAVE
*Jan 12 11:34:17.732: SW1: OSPF-2 ADJ   Vl3112: Nbr 20.60.60.60: Summary list built, size 95
*Jan 12 11:34:17.732: SW1: OSPF-2 ADJ   Vl3112: Send DBD to 20.60.60.60 seq 0x6A7E opt 0x52 flag 0x2 len 1252
*Jan 12 11:34:17.740: SW1: OSPF-2 ADJ   Vl3112: Rcv DBD from 20.60.60.60 seq 0x6A7F opt 0x52 flag 0x3 len 1252  mtu 1500 state EXCHANGE
*Jan 12 11:34:17.740: SW1: OSPF-2 ADJ   Vl3112: Send DBD to 20.60.60.60 seq 0x6A7F opt 0x52 flag 0x2 len 712
*Jan 12 11:34:17.752: SW1: OSPF-2 ADJ   Vl3112: Rcv DBD from 20.60.60.60 seq 0x6A80 opt 0x52 flag 0x1 len 712  mtu 1500 state EXCHANGE
*Jan 12 11:34:17.752: SW1: OSPF-2 ADJ   Vl3112: Exchange Done with 20.60.60.60
*Jan 12 11:34:17.752: SW1: OSPF-2 ADJ   Vl3112: Synchronized with 20.60.60.60, state FULL
*Jan 12 11:34:17.752: %OSPF-SW1-5-ADJCHG: Process 2, Nbr 20.60.60.60 on Vlan3112 from LOADING to FULL, Loading Done
*Jan 12 11:34:17.752: SW1: OSPF-2 ADJ   Vl3112: Send DBD to 20.60.60.60 seq 0x6A80 opt 0x52 flag 0x0 len 32
*Jan 12 11:34:57.752: SW1: OSPF-2 ADJ   Vl3112: Nbr 20.60.60.60: Clean-up dbase exchange
*Jan 12 11:35:07.068: SW1: OSPF-2 ADJ   Vl3112: 20.60.60.60 address 10.1.1.225 is dead
*Jan 12 11:35:07.068: SW1: OSPF-2 ADJ   Vl3112: 20.60.60.60 address 10.1.1.225 is dead, state DOWN
*Jan 12 11:35:07.068: %OSPF-SW1-5-ADJCHG: Process 2, Nbr 20.60.60.60 on Vlan3112 from FULL to DOWN, Neighbor Down: Dead timer expired
*Jan 12 11:35:07.068: SW1: OSPF-2 ADJ   Vl3112: Neighbor change event
*Jan 12 11:35:07.068: SW1: OSPF-2 ADJ   Vl3112: DR/BDR election
*Jan 12 11:35:07.068: SW1: OSPF-2 ADJ   Vl3112: Elect BDR 2.7.7.7
*Jan 12 11:35:07.068: SW1: OSPF-2 ADJ   Vl3112: Elect DR 2.7.7.7
*Jan 12 11:35:07.068: SW1: OSPF-2 ADJ   Vl3112: Elect BDR 0.0.0.0
*Jan 12 11:35:07.068: SW1: OSPF-2 ADJ   Vl3112: Elect DR 2.7.7.7
*Jan 12 11:35:07.068: SW1: OSPF-2 ADJ   Vl3112: DR: 2.7.7.7 (Id)
*Jan 12 11:35:07.068: SW1: OSPF-2 ADJ   Vl3112:    BDR: none
*Jan 12 11:35:07.068: SW1: OSPF-2 ADJ   Vl3112: Reset flush timer
*Jan 12 11:35:07.068: SW1: OSPF-2 ADJ   Vl3112: Remember old DR 20.60.60.60 (id)
*Jan 12 11:35:12.360: SW1: OSPF-2 ADJ   Vl3112: Rcv pkt  src 10.1.1.225 dst 10.1.1.224 id 20.60.60.60 type 4 if_state 5 : ignored due to unknown neighbor
*Jan 12 11:35:14.876: SW1: OSPF-2 ADJ   Vl3112: 2 Way Communication to 20.60.60.60, state 2WAY
*Jan 12 11:35:14.876: SW1: OSPF-2 ADJ   Vl3112: Neighbor change event
*Jan 12 11:35:14.876: SW1: OSPF-2 ADJ   Vl3112: DR/BDR election
*Jan 12 11:35:14.876: SW1: OSPF-2 ADJ   Vl3112: Elect BDR 0.0.0.0
*Jan 12 11:35:14.876: SW1: OSPF-2 ADJ   Vl3112: Elect DR 20.60.60.60
*Jan 12 11:35:14.876: SW1: OSPF-2 ADJ   Vl3112: Elect BDR 2.7.7.7
*Jan 12 11:35:14.876: SW1: OSPF-2 ADJ   Vl3112: Elect DR 20.60.60.60
*Jan 12 11:35:14.876: SW1: OSPF-2 ADJ   Vl3112: DR: 20.60.60.60 (Id)
*Jan 12 11:35:14.876: SW1: OSPF-2 ADJ   Vl3112:    BDR: 2.7.7.7 (Id)
*Jan 12 11:35:14.876: SW1: OSPF-2 ADJ   Vl3112: Nbr 20.60.60.60: Prepare dbase exchange
*Jan 12 11:35:14.876: SW1: OSPF-2 ADJ   Vl3112: Send DBD to 20.60.60.60 seq 0x1F37 opt 0x52 flag 0x7 len 32
*Jan 12 11:35:14.876: SW1: OSPF-2 ADJ   Vl3112: Set flush timer
*Jan 12 11:35:14.876: SW1: OSPF-2 ADJ   Vl3112: Remember old DR 2.7.7.7 (id)
*Jan 12 11:35:14.876: SW1: OSPF-2 ADJ   Vl3112: Neighbor change event
*Jan 12 11:35:14.876: SW1: OSPF-2 ADJ   Vl3112: DR/BDR election
*Jan 12 11:35:14.876: SW1: OSPF-2 ADJ   Vl3112: Elect BDR 2.7.7.7
*Jan 12 11:35:14.876: SW1: OSPF-2 ADJ   Vl3112: Elect DR 20.60.60.60
*Jan 12 11:35:14.876: SW1: OSPF-2 ADJ   Vl3112: DR: 20.60.60.60 (Id)
*Jan 12 11:35:14.876: SW1: OSPF-2 ADJ   Vl3112:    BDR: 2.7.7.7 (Id)
*Jan 12 11:35:14.884: SW1: OSPF-2 ADJ   Vl3112: Rcv DBD from 20.60.60.60 seq 0x6A82 opt 0x52 flag 0x7 len 32  mtu 1500 state EXSTART
*Jan 12 11:35:14.884: SW1: OSPF-2 ADJ   Vl3112: NBR Negotiation Done. We are the SLAVE
*Jan 12 11:35:14.884: SW1: OSPF-2 ADJ   Vl3112: Nbr 20.60.60.60: Summary list built, size 95
*Jan 12 11:35:14.884: SW1: OSPF-2 ADJ   Vl3112: Send DBD to 20.60.60.60 seq 0x6A82 opt 0x52 flag 0x2 len 1252
*Jan 12 11:35:14.892: SW1: OSPF-2 ADJ   Vl3112: Rcv DBD from 20.60.60.60 seq 0x6A83 opt 0x52 flag 0x3 len 1252  mtu 1500 state EXCHANGE
*Jan 12 11:35:14.892: SW1: OSPF-2 ADJ   Vl3112: Send DBD to 20.60.60.60 seq 0x6A83 opt 0x52 flag 0x2 len 712
*Jan 12 11:35:14.900: SW1: OSPF-2 ADJ   Vl3112: Rcv DBD from 20.60.60.60 seq 0x6A84 opt 0x52 flag 0x1 len 712  mtu 1500 state EXCHANGE
*Jan 12 11:35:14.900: SW1: OSPF-2 ADJ   Vl3112: Exchange Done with 20.60.60.60
*Jan 12 11:35:14.900: SW1: OSPF-2 ADJ   Vl3112: Synchronized with 20.60.60.60, state FULL
*Jan 12 11:35:14.900: %OSPF-SW1-5-ADJCHG: Process 2, Nbr 20.60.60.60 on Vlan3112 from LOADING to FULL, Loading Done
*Jan 12 11:35:14.900: SW1: OSPF-2 ADJ   Vl3112: Send DBD to 20.60.60.60 seq 0x6A84 opt 0x52 flag 0x0 len 32

best regards

Tomas

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