Production use of carp?

Patrick Lamaiziere patfbsd at
Thu Jun 2 22:27:24 UTC 2011

Le Thu, 2 Jun 2011 16:39:40 -0400,
John <jwd at SlowBlink.Com> a écrit :


>    However, if system A is the MASTER, and system B is rebooted,
> the carp interface on system A will flip/flop going down and
> coming back up which is not what I want.

I saw this if the switch connecting the two systems takes some time to
forward packets when a link is "up". This happens if the switch is doing
some spanning tree protocol. (on cisco swith you should use an option
"spanning tree port fast" on the switch port to avoid this)

>    This leads to my question, am I missing something simple about
> using carp?  Should I implement my own control interface on the
> private network and not use carp? What are other folks doing?

You may want to implement your own control because if the two hosts
cannot communicate, you will have two masters. This can happen if the
links on the both hosts are up, but none packet are forwarded (ie the
switch connecting the two boxes is broken in some way).

Instead writing your own script, you may use ifstated (in the ports

I've not tried FreeBSD with carp but we are very happy at $WORK with
carp on OpenBSD. I guess that should work fine on FreeBSD too.


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