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Re: [Openvpn-users] MULTICASTs: cannot join a multicast group across the OpenVPN link. Why?

  • Subject: Re: [Openvpn-users] MULTICASTs: cannot join a multicast group across the OpenVPN link. Why?
  • From: Les Mikesell <lesmikesell@xxxxxxxxx>
  • Date: Sun, 10 Sep 2006 14:25:52 -0500

On Sun, 2006-09-10 at 10:05, Tony wrote:

> > I think it means that nobody else has done it.
> Let's hope so.
> > ...everything did work as I expected with the static multicast router  
> > smcroute.
> Where can I read about smcroute? What's that?
> I need to securely tunnel a UDP stream from one LAN to another across the  
> internet. Wha would you suggest?
> Currently my OpenVPN server is a windows box but I do plan to use two  
> Linksys's WRT54GL with OpenWRT firmware which is LINUX v2.4.30. One  
> WRT54GL in each LAN, acting as OpenVPN client and server.

I set up a point-to-point tunnel with OpenVPN between two
linux 2.4.x boxes.  Ifconfig showed multicast enabled by
default so I didn't have to do anything special for that.

Smcroute (http://www.cschill.de/smcroute/) is a static
multicast router so you have to specify the source IP as
well as the multicast group to forward.  This works fine for
data distribution from one or a few known sources but wouldn't
handle dynamic changes well. 

You just start the daemon with:
smcroute -d
wait few seconds for it to set up, then specify the
join on the listening interface like:
smcroute -j eth0
and add the route to forward:
smcroute -a eth0 tun0
with the source interface, source address, group address and
destination interface respectively.   On the other end you'd
be forwarding from tun0 to eth0 instead.

  Les Mikesell

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