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I have two networks that I would like to be connected to simultaneously, but need a way to force specific applications to use a specified network connection. Are there any tools available (preferably with an easy GUI) that will allow me to set this up on a per application basis?

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which platform? – fretje Aug 7 '09 at 17:29
up vote 1 down vote accepted

You will need to setup the default route for all Internet traffic on your unlocked path.

The trick is to explicitly setup routes for all the end-points reachable only on the locked network to use the interface wired to that.

On the comment.
I am assuming that you have a dual homed host with internal and external networks wired to two different interfaces. For that the interface selection has to be done on the local host.

But, if there is a single interface path to the router appliance which splits two ways (the locked and unlocked network paths), you need to setup such routing on that device.

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If using a NAT router/firewall appliance. The static routes can almost always be configured via the router's admin web site. – Jeff Leonard Aug 7 '09 at 17:45
Static route can also be added at the workstation with the command line"route add". That is what I was getting at above. – Axxmasterr Aug 7 '09 at 18:09

The easiest way to do this is to just have separate address spacing for the two networks. The TCP/IP protocol will handle the hard work. An example would be one network uses a 192.168.x.x address while the second network is configured to use a 10.x.x.x address. Since these two connections would be on logically different networks, the IP stack is smart enough to determine which interface it needs to be routed through.

Now that being said, some applications provide for a explicit method to select the network interface it will use. Programs like Ethereal are good examples of this.

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The networks are already configured like that... the main problem I have is with browser traffic, etc.... one network is locked down, the other isn't...I want most traffic to go over the open network, but it has no real way of choosing – Adam Haile Aug 7 '09 at 17:31
You can use your default gateway as a means to force it through the open link versus the one you have locked down. Basically you want your "any any" route to go through the Default Gateway and the other network is reachable because it is on the second network. type "route print" from your CMD shell and see how you are configured to route presently. – Axxmasterr Aug 7 '09 at 17:44

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