[Openswan Users] 2 DSL Connections

Alain RICHARD alain.richard at equation.fr
Thu Dec 23 09:41:16 CET 2004

Le 23 déc. 04, à 09:21, Sebastian Haas a écrit :

> Hash: SHA1
> Hello List,
> we have 2 DSL connections (both have a dynamic IP):
> PPP0 (VPN Connection)
> PPP1 (Internet Connection, default gateway)
> ...
> If i set the default gateway to PPP0 everything works fine, but if PPP1
> is the default gateway it didn't work. But in the logs there is
> something like "sending XYbytes through PPP0". If i setup a route where
> i use the IP of the peer as destination and interface PPP0 it works, 
> but
> thats not are solution.
> Our network setup looks like:
> NETWORK ONE (OpenSWAN Linux2.4)      Network TWO (OpenSWAN Linux2.6)
> ~             PPP0 <--->              <---> PPP0
> ~                          Internet
> ~             PPP1 <--->
> Any ideas?

This is because the ESP packets are sent using the default route (PPP1) 
and not PPP0, and that probably there is no mean for the second 
provider to properly route trafic using the adress the first provider.

You have to setup the routing process on your linux box in order to use 
the PPP0 interface for all trafic emitted with the address of the PPP0 
interface (IKE and ESP trafic) and use PPP1 interface for all other 

Use iproute2 package (ip route command) to do that. See "Linux Advanced 
Routing and Traffic Control Howto" at http://lartc.org/


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