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Date: Sat, 26 Jul 2008 14:50:03 GMT
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To: freebsd-net@FreeBSD.org
From: Stephan Eisvogel <eisvogel@seitics.de>
Cc: 
Subject: Re: kern/125816: [carp] [bridge] carp stuck in init when using
	bridge interface
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The following reply was made to PR kern/125816; it has been noted by GNATS.

From: Stephan Eisvogel <eisvogel@seitics.de>
To: bug-followup@FreeBSD.org
Cc:  
Subject: Re: kern/125816: [carp] [bridge] carp stuck in init when using bridge interface
Date: Sat, 26 Jul 2008 16:40:08 +0200

 For the ADHS crowd: Using a bridge as carped device adds ~900ms to
 configured advertising interval.
 
 A chap from bsdforums has sent me a note that layer 2 failover is
 best done with spanning tree and not carp but as I explained I am
 not trying to cluster filtering bridges but cluster routers that
 happen to have a bridge sitting on top (in my case an Ethernet
 10/100 vr(4) and an Atheros card ath(4) bridged to create a
 wireless access point).
 
 I am back to 7-STABLE and also now have carpdev patch by max in
 kernel which I just merged into fib changes of julian. Because if
 it's broken why not brake it some more while at it...
 
 Using another PC with wireshark as reference I measured the inter
 packet gap of the announcements when carping the bridge and a
 setting of advbase 1 advskew 0 delivers 1.950s intervals instead
 of 1.000s as expected. When I up the advbase value to 3 the master
 will announce every 3.950s so the effect appears to be an offset
 and not multiplicative. It also does not appear to matter how
 many devices are attached to the bridge. The moment I set the
 carped interface to a physical interface announcement interval
 will come down to the correct 3.010s interval.
 
 I measured ping delay to exclude the possibility of the Alix'
 hardware timer running at wrong speed but inter packet gap was
 very near 1s for a default ping.
 
 I'll be trying to nail the thinko or bug and submit a patch
 but because I never tweaked the carp or bridge code don't
 bet on it...