MAC addr takeover

Michael Rowan mtr at
Fri Oct 16 14:33:57 MDT 1998

Flavius Bindea wrote:
> Hi,
> I'm new on this mail list and I don't have many knowledge about
> HA, but this is a very interesting feature.
> Why should MAC takeover be implemented. Is IP takeover not
> enough ?

IP takeover suffers from ARP cache updates.  Client
machines, sometimes numbering in the hundreds or thousands,
all are communicating with the server.  This means they have
the MAC address for the desination IP address in their arp
cache.  When the IP takeover happens, all of these entries
must be purged, either by hand, through gratuitous arps, or
by timing out.  None of the easy solutions work for all
platforms, so its a pain in the ass.

When you fail both the IP and MAC address over, its a win
since you don't care about the ARP cache entries.  They all
are still valid. 


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