Redundant network router setup?
Michael K. Smith - Adhost
mksmith at adhost.com
Tue Aug 14 09:10:38 PDT 2007
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> -----Original Message-----
> From: owner-freebsd-questions at freebsd.org [mailto:owner-freebsd-
> questions at freebsd.org] On Behalf Of Chuck Swiger
> Sent: Monday, August 13, 2007 5:20 PM
> To: Modulok
> Cc: freebsd-questions at freebsd.org
> Subject: Re: Redundant network router setup?
> On Aug 13, 2007, at 4:59 PM, Modulok wrote:
> > QUESTION: Is there a way to setup a redundant router, such that I can
> > offload traffic from the primary router to another machine, without
> > breaking TCP sessions?
> There are several ways of setting up such redundancy; the common case
> which Cisco calls VRRP, you can use under FreeBSD as CARP. However,
> this approach is limited to pure routing; it does not handle
> replicating the NAT state tables:
> > BACKGROUND: I have a FreeBSD machine acting as a gateway, running
> > natd(8) through ipfw(8).
> ...which you mention you are using. I don't know of any way to
> provide redundancy for existing connections going via natd.
This may require a bit of a modification, but we use two boxes running PF with CARP interfaces and PFSync to maintain state tables in the event of a failure. We use them in a failover setup but you can also set them up to load balance. In either case, PFSync takes care of the state tables quite well.
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