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[Openvpn-users] Controlling routing table with bridge mode connection

  • Subject: [Openvpn-users] Controlling routing table with bridge mode connection
  • From: openvpn2@xxxxxxxxxxxxxxxxx
  • Date: Wed, 6 Feb 2008 18:45:10 -0500

Hi folks:

I've got a question regarding controlling the routing table with a  
bridge mode connection under WinXP.  I have two OpenVPN connections  
setup for my laptop, one for UDP mode and one for TCP mode.  I use the  
TCP mode one, which is configured for port 80 so that it can get past  
restrictive policies at some hotspots, only when the UDP version won't  
work.  However, I've found that I have an issue with some DLINK video  
cameras that use UDP to send the video stream.  When I try to send the  
stream over a UDP OpenVPN connection they don't work right.  I have to  
use the TCP connection to get the stream to transmit.  What I'd like  
to do is setup another TCP configuration file that would just route  
the traffic to and from the specific IP addresses of the DLINK cameras  
over the TCP connection and leave the rest running on the UDP  

I tried manually changing the routing table on the laptop client, but  
for some reason if I try to modify any of the routes created by the  
OpenVPN connection on the laptop, WinXP always says it couldn't find  
the route, even though I typed it in correctly (I've tried this a  
number of times and I'm now wondering if OpenVPN has done something to  
protect the routes it creates by default from being manually modified  
after the fact).  It looks like my only choices in the bridge  
connection are to route traffic for the entire subnet through the  
tunnel, or route everything through the tunnel, but I'm unable to  
control it any finer than that.  I was also looking for a way to  
modify the default metric value chosen by OpenVPN of 30, figuring that  
even if I open both a TCP and UDP connection to the same host subnet,  
if I could lower the priority of the TCP route for the generic subnet,  
and then manually add extra routes for the specific IP addresses of  
the cameras, then that could work as well.  However, I've been unable  
to find any method to control the default metric either.  It looks  
like the route-metric directive only applies to extra routes added in  
the config file, not the ones OpenVPN creates by default.

I suppose I could try to setup a routed connection in addition to a  
bridged one in order to accomplish what I want, but before I went  
through that trouble I thought I'd try to make it work with the bridge  
connections I already have setup on the server side.

Suggestions welcome.


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