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Problems with Multihomed server

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by ewai

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I have installed an NT4.0 sp6 server with two NICs. I am only using IP. I have enabled IP forwarding, and installed RIP for IP. My intention is to use this machine as a gateway from one subnet to another 10.1.x.x and 10.2.x.x, both with mask 255.255.0.0. However I cannot route IP across this server. I have tried adding gateways for one, then both NICs (using the other NIC as the gateway address) with no joy. I have even tried using multiple IP addresses on one card, but also to no avail. The server can happilly PING anything, on either side, and a client on either side can ping as far as the NIC in the sever attatched to their subnet. Am I missing something fundamental here?

3 replies

by some guy in seattle

You should only ever have to add one default gateway address to a multi-homed device. This is the "gateway of last resort" and is where the machine will send traffic that it doesn't know about. If this machine is not going to access anything otherthan your 10.1 and 10.2 subnets (the internet for instance), then you will not need a default gateway address.

Sounds like you need to make sure that all your devices are pointed to this gateway. All the 10.1 devices need to have the this NT machines address as their gateway and the same for the 10.2 devices. If any of these machines are going to access the internet *not* using this NT machine as an intermediary device, then add the routes manually. For instance:

Set the default gateway to the internet capable gateway and a manual route to the 10.x.x.x by

route add -p 10.x.x.x mask 255.255.0.0 10.x.x.x 1

The "-p" makes it persistent during reboots, substitute the first 10.x.x.x with the remote network and the second 10.x.x.xas the gateway NIC on the local subnet. The last "1" is the hop count.

Hope that helps -

by ewai

Thanks for that. As I am currenlty in testing I only have one client attatching to either side, I am not using internet access at all in this situation. Both are using default gateways which are the address of the NIC in the server on their subnet. However still there is no joy. Although the server is configured for routing it just won't route. When I add the gateways to the clients then PING the other subnet they timeout, as if they are going to work, but even if I use "-t 5000" still no response. Without a gateway the PING responds with Destination Host Unreachable. This is why it makes me think there is a problem in the server config not the client, it's as if the two NICs are not tallking...

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