Routing applications to certain network cards

[sjau]

Hiho

I think I have a difficult question:

I have two network cards (1 wifi & 1 ethernet). At home I can connect with the wifi card to my uni-network or I can use my normal internet access by ethernet/wifi.

Now, the uni-network is limited but very quick. The normal inet access is not limited but, compared to the uni-network, slow.

How could I make now that certain programs use exclusively only one of the network cards? E.g. browser, email, ... only use the wifi-card connected to the uni network
And stuff like irc (is blocked at university) only use my normal ethernet card with my normal inet access?

Currently I'm using Ubuntu Feisty.

[falko]

Hm, good question. Maybe this can be done with iptables?

[sjau]

well, I think it can be done with iptables since the applications use specific ports but I haven't ever played around with iptables.

Another thing I stumbled accross is "socks" but I'm not sure if I get the concept of what that is.

[geekman]

I think you might be able to do something like this?

Make website traffic go through eth1
iptables --insert OUTPUT 1 --dport 80 --jump ACCEPT --out-interface 'eth1'

Make Bit Torrent go through eth0

iptables --insert OUTPUT 1 --dport 6881 --jump ACCEPT --out-interface 'eth0'

Though this is totally untested and iptables may not even like that syntax of using dport...not sure. I just based it off some routing I already to with IPTables where I say: if traffic is coming from here and going to there use this interface.
if traffic is coming from somewhere else and going here then use this interface instead.

Just a note, you'd want basically the same rules but for the source port also so both incoming and outgoing traffic goes through the right Interface. A further edit you'd need to use --in-interface instead for these rules...just a guess, and there might be a more efficient way of doing it too i.e. only needing one rule per port.

Thanks.