Connecting a win2k server to two different ADSL lines.

September 11, 2005 5:19 AM

I want to connect two ADSL lines with different IP ranges to a server.

This is to allow external sources to connect to one of two completely different ip addresses for the same server. I thought it'd be as easy as connecting an extra network card, but this isn't the case. The network cards work individually, but will not work together. I suspect that return traffic is always routed via the default gateway.
I am using Windows 2000 servers. Application served include http and rdp (port 3389)
Is there any way to allow traffic to come to the same server via different ADSL lines?

posted by seanyboy to computers & internet (3 comments total)

I have a virtually identical setup, except for the windows server. We have two stand-alone ADSL modem/routers (well one is ADSL, the other is NTL Cable), which both have static IP's, and are both connected to the LAN. The computer and both routers have private IP addresses on the same 192.168.1.0/24 network. TCP connections that come in from either of the boxes seem to go back out through the box that they came in on.

For example, TeamSpeak users can connect in on either IP, as both modem/routers have their port forwarding setup to forward to the internal TS server. Connections that originate from inside the network, or on the TS server will go out through the default route.

I suspect with windows, you would need to allow routing on all three interfaces. You'd need one for each card and one for your internal network. Alternatively, spend a few £ on some combined routers. They work for us.
posted by gaby at 6:26 AM on September 11, 2005

We did something like this under unix with our firewall and had to do it via some routing rules. I have no idea how to do this under windows. If all else fails you can build a router fairly cheap and run linux on it. We did this with a regular unix box at first but eventually found out that our regular firewall software (the free linux software, shorewall) did this natively.
posted by RustyBrooks at 6:48 AM on September 11, 2005

Thanks for the info. Strangely, after puzzling over this for the larger party of a day I discovered that it had been working all along (except) from machines in one of the two defined subnets.
posted by seanyboy at 8:43 AM on September 11, 2005