[Firehol-support] Forwarding through multiple uplinks/providers

Carlos Rodrigues carlos.efr at mail.telepac.pt
Wed Aug 15 12:21:47 BST 2007

On 8/13/07, Mirko Buffoni <firehol at synthesys.it> wrote:
> Basically what I'm trying to solve, is to reach the internal pc through one
> of the other uplinks available, if unfortunately the gateway that gives
> access to internet goes down for some reason.

The uplinks are all connected to the same box/router?

If I understand correctly, when you have both links active, connecting
from outside to the secondary link's address on a port that redirects
to an internal machine doesn't work, because the replies are sent
through the primary link (which is the router's default gateway).

Well, if you need this only in case of failure on the primary link,
then the only thing needed is for the router to switch default
gateways when the link goes down.

Otherwise, for this to work the router must have a rule forcing all
traffic coming from the internal pc, and not directed to the router's
internal address to be routed through the secondary link. Im not sure
you can do this with iptables/firehol (or even if you want to), but
that should be possible with routing rules (using the "ip route"

Carlos Rodrigues

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