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Lunatik
Asked: 2014-10-11 06:46:58 +0800 CST

Dual NICs, dual ISPs, dual FTP servers - Can't keep both connections running. What am I doing wrong?

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I have a Windows Server 2003 machine with dual NICs. Until now we've only had a single ISP provisioned by our landlord in the building and have only been using one NIC. Filezilla is the FTP server.

We've had a long standing issue with a client who needs to use a very specific VPN setup provided by an ancient Cisco router. Trouble was this router refused to co-exist with some other clients' VPN settings, meaning we frequently had to swap cables to bring the old VPN in and out of action.

This, as you can imagine, got very old.

We've got a new ISP which is dedicated for us and the plan is to leave the Cisco VPN running on the old ISP and move all other clients over to the new connection. The thinking being we would run the office network on a separate subnet off NIC 1 and leave only the Cisco VPN connected to NIC 2. Running two instances of Filezilla binding to specific NICs should allow FTP to be provisioned on both internet connections.

This all works fine and both FTP servers are accessible from the internet...providing only one is active at a time. As soon as one is connected the other server can't be reached.

I can see how the server might have trouble routing to two external connections, deciding which gateway to use and what not, but I'm pretty much at my knowledge limit about such things so don't know where to turn next.

Do I have to look at defining routing within Windows (RIP?) so that it can route to both gateways simultaneously?

windows-server-2003

2 Answers

  1. Windows does not support multiple default gateways.

    Since this client is connecting to the Cisco router via VPN they can have their own IP address on the network (they'll need to be given an address on the same subnet the server is configured to use on the second NIC). If you have it configured this way then you can simply remove the default gateway on that NIC and it should work.

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  2. Best Answer

    OK, thanks to joeqwerty's comment I got there.

    I had to delete one of the default gateways that was defined against one of the NICs as both suggested, leaving 192.168.1.1 as default on one, but the key was to define a persistent route to the other subnet gateway as follows.

    Address     Netmask     Gateway
0.0.0.0     0.0.0.0     192.168.1.2

    When I saw it set up and the bytes started flowing (a welcome sight at 4.45 on a Friday!) it actually made perfect sense. Thanks to all.

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