Force an application (or port) to use a specific network interface..

[dawks]

I have two network adaptors, each of which goes to to a separate ISP, and I'd like a certain application to use a specific ISP for its needs. Is there a way to force it to use that adaptor (the application itself has no tool for this)? It uses a certain TCP port which I could specify.. Thanks.

 

[postmortemIA]

it might be hard coded if it is not offered as option to change/

 

[cleverhandle]

I don't think there's any general-purpose way to accomplish this sort of thing - it runs counter to the design of TCP/IP. Applications aren't supposed to care about things like how packets are routed - they just feed the OS some data, a port, and a destination and say "do it". And the part of the OS that does routing decisions isn't supposed to care what's in the packet - it only looks at the address.

If you can figure out exactly what destinations the application is sending to, you could set a static route for those destination IP to be routed through the alternate ISP. But I think you'll need to deal with this at the IP level and not at the application level.

 

[Cerb]

If you can separate them by IP, protocol, and/or port, a junker PC w/ 3+ NICs and a multiWAN firewall might do the trick...but beyond knowing they exist, I can't help further, there 🙂.

 

[cleverhandle]

Originally posted by: Cerb
If you can separate them by IP, protocol, and/or port, a junker PC w/ 3+ NICs and a multiWAN firewall might do the trick...

It might be doable by something like PF or iptables, but even then I don't think it would be easy. At best, the "EZ firewall" distros will let you prioritize traffic, but changing the routing on the fly is a trickier problem.

 

[nweaver]

the ability to bind to an IP address has to be supported in the app, otherwise you are stuck with trying to use route statements to do this, and that can get ugly quick.