Using Windows Server 2008 R2 as a router

IF this server has interfaces on both network you can route this at the dafult gateway of each subnet:

GW-A: route add dest network -> Win2008R2 server / GW-B: route add dest network -> Win2008R2 server

And enable ip routing at the server: http://technet.microsoft.com/en-us/network/bb545655

Hope it helps.

The reason for the warning is that if you have multiple ips configured, say, 192.168.1.10 and 192.168.99.10 and two routers on this network (192.168.1.1 and 192.168.99.1) then all responses will go out over one of the routers until it fails to respond (arp doesn't resolve).

It won't balance the traffic over the two.

This will also have a side effect that connections coming in on the 192.168.1.1 router (say with a public ip of 123.123.1.1) will go out on the 192.168.99.1 router (say with a public ip of 123.123.99.1) so someone connecting to 123.123.1.1 will get a response from 123.123.99.1 .... i.e it won't work.

You need a more intelligent firewall/router to do this sort of thing.

How you move ip's between the server is probably not important if you are trying to achieve redundancy. You have a networking issue which windows is not really equipped to resolve and it would be better not to try. Inbound and outbound load balancing/redundancy networking equipment is not really expensive until you get to high end and it will cost you less in time.