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Re: CARP and switches



On Fri, Sep 30, 2005 at 04:40:26PM +0200, Henning Brauer wrote:
> * Charles Sprickman <[email protected]> [2005-09-29 22:51]:
> > The design seems to assume that one MAC address can 
> > only exist on one port at a time, correct?
> 
> no, not at all. There have been so-called multicast MAC addresses from 
> the stone age on, and that is what carp uses.
Actually, the carp virtual mac address is not a multicast address. Only
the carp advertisements use multicast.
The switch knows where to send the packet because the master carp host
sends out gratuitous arp replys and carp advertisements with the carp
virtual address as the source, so unless you have a horribly broken or
misconfigured switch, it Just Works(tm)