[Voyage-linux] Re: [Madwifi-users] Weirdness - 12 second dropouts every 4 minutes

[Matt Brown]

On Mon, 2005-11-21 at 17:32 -0500, Edwin Whitelaw wrote:
> Update on things...
> 
> Seems it's *not* a wireless or madwifi issue.  I have determined that 
> the zebra daemon on the NRVU box is resetting but it does not correlate 
> to any observed RF variations or link status, etc.  Making my life 
> further confused, I am running quagga (zebra +ospf) on the other two 
> WRAPs and they are working fine.  Everything is the same that I can 
> determine so far.

OK. 

When I saw the title of your post a while back I thought "that's exactly
what we're seeing", but I didn't post because I didn't realise you were
using OSPF until this post. 

We see the exact same problem and have tracked it down to the madwifi
driver dropping multicast packets every now and again. This causes OSPF
to lose some hellos and the link adjacency goes down. In our case with
hellos being sent every 10 seconds, OSPF would lose 4 hellos in a row
and receive a hello just as the dead-timer fired. Hence the adjacency
was only down for 10-12 seconds. 

To work around it we've dropped the hello-interval down to 5 seconds and
upped the dead-timer a bit. This significantly improves OSPFs ability to
handle the lost multicast packets.

We're still using the old madwifi driver, so I wasn't going to report
this until I had had a chance to try madwifi-ng and see if the behaviour
was still apparent. 

I can provide tcpdumps etc if needed. 

Kind Regards

-- 
Matt Brown
matt at mattb.net.nz
Mob +64 275 611 544 www.mattb.net.nz