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i2mc

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Problem with routing on dual-homed windows 2003 server, linux can do this, can windows?

Some TCP routing on windows assistance would be much appreciated ...

My scenario is this;

I have a windows 2003 server in a datacentre with dual NIC's. NIC1 sits on 172.16.1.xxx and uses gateway (1) 172.16.1.3 (the default at present). NIC2 sites on 172.16.2.xxx and has gateway (2) 172.16.2.1 available to it but not configured as a default and only confugured by a ROUTE command shown below.

Both gateways can route to the internet over totally diverse paths. and both gateways use NAT to expose the server on its appropriate external IP address.

Is it possible to get the server configured such that packets coming in via NIC1 are routed out on NIC1 / Gateway 1 while packets that arrive on NIC2 are routed out on NIC2 / Gateway 2?

Although I have added a route for the second gateway (route add 172.16.2.0 mask 255.255.255.0 172.16.2.1), this doesn't seem to be enough info to tell the windows machine how to route out packets that have arrived on NIC2 but are going back out to the internet. I am assuming at present the server is routing them out on the default gateway (1) and hence pinging the system from the outside world on it's second external IP address doesn't work.

I have verified that the second route works by swapping the default gateway - I can then ping it only on the second external IP and the first stops working.

In linux I can do this with the routing tables and hence can have a server reachable via 2 public IP addresses. We use this for testing alternate firewall configurations and diagnostics as we have an intermittant fault on some routes at present.

Is this possible in windows? I've googled as much as I can but can't seem to find a definitive answer. I'm almost certain I had this working last year but can't for the life of me figure out what is wrong this time (or maybe I was dreaming!).

Advice appreciated.

Thanks
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Rob Williams
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i2mc

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So to be 100% clear on this, if I have 1 server with 2 NIC's each NIC connected to a different gateway, if those gateways both use NAT to enable the server to have a public IP address (via different ip transit providers), then it will NEVER be possible to ping public_ip_1 AND public_ip_2 at the same time and get a response? I will only ever be able to do it to the public_ip that gets routed via the "default" gateway?

Is that right?

Seems a bit limiting ... and frustrating that it is so different from linux, but I guess that's life!

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Thanks i2mc.
Cheers !
--Rob