Networking - CARP interfaces

Daniel Gerzo danger at
Wed Jun 15 11:42:18 UTC 2011

 On Tue, 14 Jun 2011 17:01:21 -0400, Steve Polyack wrote:

>>>> I'll just have to adapt and ensure they have the same IP addresses 
>>>> then.
>>> I have a suspicion that the important part may be the number of IP 
>>> addresses on the CARP interface.  If CARP sends an advertisement from 
>>> each IP alias on a CARP interface, then I think that would explain 
>>> what you are seeing - and also possibly give you a workaround by 
>>> adding two more bogus IPs on your primary datacenter firewalls (where 
>>> IPs W and Z are normally missing).
>>> - Steve
>> I'll give it a try, although I think in a scenario where the carp 
>> interfaces have the same number of IPs and these IPs differ, both 
>> interfaces will claim mastership.
>> Will post results.
> Now that I look at the spec, it looks like both the count and the
> addresses themselves are provided in VRRP packets.  CARP likely does
> the same.  I can't speak for whether these things are considered 
> along
> with the VHID and password, but it's worth a shot.  I think you are
> correct, though.

 CARP does the same and should you have different IP addresses on the 
 master/backup machines they will misbehave.
 I think the way to solve this issue is to split the two other IP 
 addresses onto a separate carpN interface...

 Kind regards

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