CARP across two jails on one host?

Nikos Vassiliadis nvass9573 at
Sat Jul 24 09:54:54 UTC 2010

On 7/23/2010 3:09 PM, Paul Schenkeveld wrote:
> Since FreeBSD 8 jails support virtual networking (a.k.a. vimage).  It
> looks like it should be possible to do CARP between jails using vnet
> instances.  You'd need to do some network plumbing to get a virtual
> bus topology network between the jails (ng_ether probably) but I have
> not yet tried this myself.  Also, beware that virtual networking is
> still not production quality as far as I know and rc.d/jail doesn't
> know how to set it up (yet).

CARP is not virtualized for the time being...

> OTOH, is CARP the right solution for your problem?  If you would
> succeed to build the setup using vnet, CARP would only fail over if
> CARP of the master jail stops sending hello packets.  This would
> normally only occur when the master jail and vnet instance are torn
> down completely (or the CARP interface in the master jail destroyed).
> It would not kick in if the application inside the master jail stops
> responding.


CARP is designed to handle network layer failures, and such a failure
will take the physical host down. Think power or system failures...

I *believe* that the user space CARP implementation (net/ucarp) can
fire up scripts. An other candidate you should examine would be

HTH, Nikos

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