force an app to use a specific network when 2 network interfaces are active

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force an app to use a specific network when 2 network interfaces are active

Hi:

I have a client who uses an iMac. There are 2 networks in his office, one a corporate, firewalled ethernet connection and the other a standard DSL connection over Airport. Because of the company firewall protocols, he'll need to use iChat a/v over the wireless network. Is there an easy way to force iChat to specifically use the Airport interface while leaving all other applications using the ethernet interface? (PS - A step by step guide would be helpful, especially if the setup needs to be done via Terminal commands).

Thanks!

Mac Pro Octo 8, 6gb, 350gb/500gb/750gb/1TB, Mac OS X (10.6.2), FCS 7, BlackMagic Intensity Pro, Samsung 24 HD

Posted on Dec 2, 2009 10:08 AM

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Answer 1

K T

Level 7

23,895 points

Dec 2, 2009 10:26 AM in response to mcguirek

The trick is adjusting the routing tables (which doesn't depend on destination port or source app, but does depend on destination host).

Say your default gateway is 111.222.223.4 and you have a vpn which can route traffic on 666.777.888.9. You want iChat traffic to route over 666.777.888.99, so do this:

sudo route add mail.myserver.com 666.777.888.9

Some versions of route might require a "gw" keyword between the address and next hop. If you want to make a whole net route over that next hop, just add a netmask in CIDR notation for the destination, like this:

sudo route add 192.168.0.0/24 666.777.888.9

If you want to view the existing routing table, use

netstat -nrl

...or...

ip route list

Good luck....

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Answer 2

mcguirek Author

Level 1

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Dec 2, 2009 12:55 PM in response to K T

Thanks for your note, however I'm confused about a couple of things:

• Does 666.777.888.9 represent the IP address being picked up via the Airport connection or does it represent the router/gateway that Airport is connecting to? I attempted using your commands where 666.777.888.9 was replaced by the address of my router for the Airport connection. Both commands ran properly, however it still won't connect through Airport.

• In first command, you specify mail.server.com. For the purposes of iChat should this be the usual aim server, login.oscar.aol.com?

• Will the commands issued permanently update the routing table until I remove them, or are they good for that session only? Does it apply to all users or just the currently logged in user?

Thanks!

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