[j-nsp] Strange ARP issue on M7i

[Tobias Heister]

Hi,

Am 14.08.2012 22:27, schrieb Jonathan Lassoff:
> On Tue, Aug 14, 2012 at 1:20 PM, Tobias Heister <lists at tobias-heister.de> wrote:
>> Am 14.08.2012 22:09, schrieb Jonathan Lassoff:
>>> A dynamic routing protocol and BFD would be see this right away and
>>> move traffic, but this would break any static routes that rely on any
>>> dynamism with ARP and next-hops.
>>>
>>> Moral of the story, as I see it: avoid static routing.
>>
>> At least in our case it was a bgp route with a third-party next-hop (server) living on a connected LAN segment.
>> So we could not be saved by BFD in this case, but i admit its a special setup.
> 
> I'm confused, because you said that "The next-hop ip was gone for
> several weeks".
> 
> In this case, wouldn't BGP detect the neighbor as down and remove the
> route from the RIB?

The next-hop is not the neighbor in this scenario. The next-hop is a server on a connected lan segement while the bgp session is with an upstream router. The bgp neighbor was fine all the time.

Its basicly an injection setup (think of some kind of RTBH without blackholing but forwarding) Some router injects routes into bgp with subnet A pointing to server B. Server B was gone for some weeks (decommissioned) but nobody decommissioned the route pointing to the server. We found the situation while cleaning up.

As mentioned before it is a special setup in our case.

-- 
Kind Regards
Tobias Heister