From mboxrd@z Thu Jan  1 00:00:00 1970
From: Andi Kleen <ak@suse.de>
Subject: Re: determine outgoing interface (eth0,eth1) for a packet according to the dest IP
Date: Tue, 25 Apr 2006 09:43:49 +0200
Message-ID: <200604250943.49422.ak@suse.de>
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On Tuesday 25 April 2006 09:31, John Que wrote:
> Hello,
> What is the right way to determine on which interface card
> (eth0 or eth1) will a packet be sent (according to the dest IP)?

You can send a rtnetlink RTM_GETROUTE message to ask the kernel.
Result is the interface index in RTA_OIF, which can be converted
into a name.

-Andi