[PLUG] ARP black magic question

[Galen Seitz]

Eric Harrison <eharrison at mail.mesd.k12.or.us> wrote:

> One particularly complex load-balancing setup we have is in need of
> a little arp black magic: I need server A to answer arp requests on
> behalf of server B.
> 
> That is, when some random host sends out an arp query "who has serverb?",
> Server A needs to respond "serverb is at 01:02:03:04:05:06", where 
> "01:02:03:04:05:06" is the real MAC address for server B. 
> 
> I'm not having much luck figuring out how to do this and all of the
> docs I can find cover how to hijack an IP via arp & proxy arp. Neither
> of these fit my scenario. 
> 
> Has anyone here setup something like this up? Given how much trouble I'm
> having I assume there is an embarrasingly simple solution ;-)

I have used proxy arp in the distant past.  The person that wrote the
code is Russian, and the documentation is sparse, to say the least.
Here are some pointers, but I'm not sure they will be terribly useful.

/usr/src/linux/Documentation/networking/ip-sysctl.txt
http://www.stearns.org/doc/proxyarp-howto
a mailing list thread:
http://www.ussg.iu.edu/hypermail/linux/net/0004.2/0055.html


galen