[Xorp-users] OSPF point-to-multipoint issue

[Vincent, Michael - 0665 - MITLL]

> If it was OSPF, then I guess the code should be changed
> to remove the route, perhaps when it starts receiving
> broadcast pkts from the peer again?

That sounds right.

To 'resolve' the issue, we exit xorpsh and at the linux command line, issue:

for i in `route -n | grep 255.255.255.255 | awk '{print $1}'`; do route del ${i}; done

This removes all the host routes that OSPF added.  There are no host routes (mask of 255.255.255.255) in the linux kernel routing table by default.  The host routes that are added are related to those routes in Xorp OSPF configuration.

> Can you confirm that the problem happens on rejoin of the
> networks and not on link 1-3 failure?  I had asked for
> 'show neighbor' on link failure, and if that was your second
> set of dumps, then the problem appears to already exist before you
> ever get to the rejoin phase.

As the link fails, the host routes are added and OSPF peers drop.  This behavior is expected.  When we bring the link back up, OSPF does not re-establish adjacencies (your previous statement regarding "remove route [...] when it starts receiving broadcast pkts from the peer [...]") and thus the host route is not removed.  With the host route not removed, the 'neighbor' looks multiple hops away and thus not adjacent so no OSPF peering.  That's the catch-22 we eluded to earlier.

The 'show' outputs are from 1) steady state, 2) after the link is failed, 3) after the link is re-established.  Note 2) and 3) outputs are very similar as OSPF goes into the expected fail state during/after link failure.  We don't expect the results from 3) as after link recovery, we would expect the OSPF 'show' output to be similar to 1) steady state.



    Cheers.

-- 
Michael J. Vincent
Group 65 - Advanced Networks and Applications
MIT Lincoln Laboratory
244 Wood Street
Lexington, MA 02420
Office:  +1.781.981.3459


-----Original Message-----
From: Ben Greear [mailto:greearb at candelatech.com] 
Sent: Friday, June 18, 2010 4:36 PM
To: Vincent, Michael - 0665 - MITLL
Cc: xorp-users at xorp.org; Zuena, John - 0665 - MITLL
Subject: Re: [Xorp-users] OSPF point-to-multipoint issue

On 06/18/2010 12:42 PM, Vincent, Michael - 0665 - MITLL wrote:
>> So, in this case, router 1 has Full adjacency to 3, but 3 shows 1 as Down??
>> If so, that seems wrong, but maybe I just don't understand point to multi-point OSPF configs...
>
> Agreed.  Hence our dilemma.

So, if you remove a route on 3 (pointing towards 1 via router 5), it works?

What added the route to begin with..OSPF?

If it was OSPF, then I guess the code should be changed
to remove the route, perhaps when it starts receiving
broadcast pkts from the peer again?

Can you confirm that the problem happens on rejoin of the
networks and not on link 1-3 failure?  I had asked for
'show neighbor' on link failure, and if that was your second
set of dumps, then the problem appears to already exist before you
ever get to the rejoin phase.

Thanks,
Ben

-- 
Ben Greear <greearb at candelatech.com>
Candela Technologies Inc  http://www.candelatech.com