On Thu, Sep 21, 2017 at 03:45:28PM +0100, Stuart Henderson wrote:
> Two routers on a point-to-point ethernet, the link between them dropped
> out but ports stayed up. The link came back after ~2h or so but ospfd
> doesn't recover -
> 
> first router:
> 
> 195.95.187.3    1   FULL/OTHER   00:00:03 195.95.187.16   ix1       1d14h45m
> 
> Neighbor 195.95.187.3, interface address 195.95.187.16
>   Area 0.0.0.0, interface ix1
>   Neighbor priority is 1, State is FULL, 92 state changes
>   DR is 195.95.187.16, BDR is 0.0.0.0
>   Options -|O|-|-|-|-|E|-
>   Dead timer due in 00:00:03
>   Uptime 1d14h49m
>   Database Summary List 0
>   Link State Request List 0
>   Link State Retransmission List 0
> 
> 
> second router:
> 
> 195.95.187.1    1   FULL/OTHER   00:00:03 195.95.187.17   vlan730   1d14h45m
> 
> Neighbor 195.95.187.1, interface address 195.95.187.17
>   Area 0.0.0.0, interface vlan730
>   Neighbor priority is 1, State is FULL, 12 state changes
>   DR is 195.95.187.17, BDR is 0.0.0.0
>   Options -|O|-|-|-|-|E|-
>   Dead timer due in 00:00:03
>   Uptime 1d14h46m
>   Database Summary List 0
>   Link State Request List 0
>   Link State Retransmission List 1
> 
> 
> i.e. they both think that they're DR and that there's no BDR.
> (1d14h ago, yeah I was a bit slow spotting it this time..)
> 
> Not the first time I've seen it (on various links over various releases)..
> In this case they're on a /31 though I've seen it on /30's previously.
> 
> Are other people seeing this?
> 
> Does anyone have an idea where the bug might be, or a better suggestion
> than removing the interfaces from ospfd.conf, reloading, re-adding,
> reloading again?
> 

Do you have tcpdumps of the OSPF traffic by any chance?
I think there is a case where the hello protocol gets confused and so you
end up with multiple DRs that stick to themself.
You could try to down/up the interface which may be enough to get out of
this state...

-- 
:wq Claudio

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