ip aliasing, virtual interfaces and incorrect source addresses...

["Matthew Whitworth" <matthew@okcomputer.org>]

I have a host (eth0 = 10.0.30.251) to which I recently added a virtual
interface (eth0:0 = 10.0.30.249).  Now all  traffic that originates from
this host has the source address of eth0:0, which is causing some problems
with a firewall that I don't control.

The output of both the route and netstat -rn commands shows eth0 as being
the default interface.

I'm doing all my interface configuration through the
/etc/network/interfaces file and have not added any routes specifically
for the eth0:0 interface (it was just added for a virtual web server).

A friend has suggested that it is typical for an interface to choose the
numerically lowest IP address that has been assigned to it as as the
source address for outbound packets, but I haven't found anything to
support that.

Any help much appreciated!

Matthew Whitworth