[c-nsp] ARP Timeout - IP address takeover

[nick.nauwelaerts at thomson.com]

> -----Original Message-----
> From: cisco-nsp-bounces at puck.nether.net 
> [mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Paul Stewart
> Sent: Friday, January 21, 2005 10:47 AM
> To: cisco-nsp at puck.nether.net
> Subject: [c-nsp] ARP Timeout - IP address takeover
> 
> 
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
> 
> Hi there..
> 
> Our mail administrator is implementing a small mail cluster solution
> that involves  using IP takeover techniques in case of 
> failure.  So, at
> one moment an IP could belong to one MAC address but if a box 
> fails that
> IP could showup with a different MAC within seconds....
> 
> Since our core network is 100% Cisco, is there any ARP related issues
> that will delay our customers in seeing the proper MAC if a 
> mail server
> failure should happen?  Or, is there any way to control the 
> default ARP
> timeout for a specific IP address?
> 
> Thanks in advance,

Not really an answer, but we are currently using 2 different cluster
mechanisms:

1) hot failover clusters with virtual mac addresses. When one of the
nodes fails the other takes over it's IP and it's MAC addresses. Easy on
routers because the MAC address doesn't change, and a CAM update on the
switches is near instantanious as well.
2) cold failover with virtual IPs but real MAC addresses. Here we just
make sure that when one of the machines takes over we send out a few
arpings to the router to force the MAC update. This is on various
unixes, I don't know how one can do this under windows.

// nick