Switching IP aliases
I wish to have 2 nearly identical machines. Each will have it's own IP
number plus an IP alias. The idea is that I wish to occasionally take 1
down and give it's IP alias over to the other machine, so that there is no
visible change to any clients.
The problem is that machines on the localnet may have an entry in their
ARP tables with the ethernet address of the old machine at the time of the
changeover, and so be unable to reach the new holder of that IP number.
It is necessary for the new machine to send some packets with a source
address of the new alias it has taken on so that local hosts will see the
new ethernet address and update their ARP tables appropriately.
The only way I've found to do this is to alter the routing so that the new
IP alias becomes the gateway to the localnet. (host routes are then added
for the primary IP address to restore that part of things) Outgoing
packets will now have the right source address. It sends some packets out
and then switches the routing back to normal so that the IP alias is ready
to be given back. This seems to work OK, but I'd really rather not stuff
with the routing, so:
Is there a better way?
8<--------------------------------------->8
Richard Shepherd (richards@waikato.ac.nz)
8<--------------------------------------->8
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