[TriLUG] OpenVPN bridge-mode question

Brian Henning brian at strutmasters.com
Wed Jun 21 09:18:02 EDT 2006


Hiya Gang,
   Yous guys have been tremendously helpful (just like always) with my 
recent other inquiries, so I thought I might try my luck with this one 
too.  (I posted it to openvpn-users a few days ago, and no one ventured 
a reply)

I have a machine running OpenVPN that has two NICs in it.  For 
argument's sake, we'll say eth0 connects to a LAN with a 192.168.10.0/24 
subnet, and eth1 connects to a separate LAN with a 192.168.20.0/24 
subnet.  Both subnets have their own public gateways, on different ISPs. 
  All of the servers I need to reach reside on .10.0/24.

OpenVPN is configured to bind to all addresses (0.0.0.0) and hand out 
addresses in the 192.168.10.200 - .240 range.

If I configure my bridge device (br0) to bridge my tap device (tap0) to 
the NIC on .10.0/24 (eth0), and bring inbound VPN connections in on the 
same interface (via the gateway on .10), everything works as expected.

However...

If I bring an inbound VPN connection via the NIC on .20.0/24 (eth1) with 
everything else above being the same, VPN negotiation never finishes and 
the OpenVPN server logs get a bunch of "no route to host" messages.

My understanding of routing is still pretty cloudy at best..  and I have 
some vague instinct that "this makes sense, really" but can't clear it 
up in my mind.  I really need to make this work, though; I need VPN 
traffic itself to move in and out through eth1, but have it able to 
communicate with the subnet on eth0.  I also want to stick with 
bridging, if at all possible.

Hopefully my verbal description is clear enough..  I'll sketch out a 
picture of the layout if necessary.

Thanks in advance!

~Brian

-- 
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Brian A. Henning
strutmasters.com
336.597.2397x238
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