Subject: Re: Multiple default routes through different network interfaces?
To: None <>
From: Wolfgang Rupprecht <>
List: tech-net
Date: 10/23/2001 09:36:36
> Check the "ifdefault" work done by Paul Vixie and Ted Lemon a few years ago.

Caution, this is kind of a rude (but clever) hack that only works if
one has an essentially empty routing table.  If there are any
intervening CIDR entries between the target X.X.X.X/32 and
then the per-interface route entry will never be consulted.
Essentially the per-interface logic only kicks in for default.

When I was triple homed I used to have quite a few routing entries
that preferentially pushed packets this way or that.  Connections that
the local host initiated would preferentially go out the interface
that had the best connectivity to that destination.  (Essentially
anything on the ISP's network went via that ISP's interface.)
Connections that were incoming had some restrictions as to which
interface they could go out on (eg. to make it past the ISP's
anti-smurf filters.)

I found that the vixie defaults hack wouldn't work, but a one-line ipf
filter would.  YMMV

       Wolfgang Rupprecht <>
Coming soon: GPS mapping tools for Open Systems.