Re: [Openvpn-users] Re: Re: openvpn and voip

["Eric \"Skippy\" Hope" <ehope@xxxxxxxxxx>]

Charles Duffy wrote:

> On Wed, 03 Aug 2005 15:30:25 -0400, Eric "Skippy" Hope wrote:
>
>  
>
> > The clients are assigned a 10.10.10.x address by openvpn. The asterisk
> > server has a 10.11.12.13 address and a route pointing 10.10.10.x to the
> > vpn gateway.
> > The client end can ping the server; the server end can ping the client.
> > The sip registration works fine, as do the sip INVITEs all going over the
> > vpn.   Once the call recipient picks up the phone, the softphone sends a
> > sip OK packet, which has as a payload a SDP packet with the details for
> > the actual voice traffic, and this is where its sending the pubic IP
> > rather than the private IP.  All of the sip addresses are in the proper
> > format, ie sip:ext@privateip.
> >    
>
> See, I'm using softphones behind OpenVPN with an Asterisk server, and
> everything Works For Me. Frankly, I'd be curious to know how the systems
> are getting the public IPs in the first place -- tried using ethereal or
> somesuch to keep an eye on the softphone while the connection is being
> established?
>
>  
I was expecting it to Just Work.  It was a rather nasty surprise when it 
didn't.

As for how it got the public IPs, its a normal part of the voip setup.  
Once the two ends agree to talk, SDP (Session Description Protocol, rfc 
2327) is used to determine where the actual packets with the voice 
traffic go.  We'd pick up the phone but the line was dead air since the 
voice data never arrived.  As far as asterisk new everything was fine 
and dandy, but it wasn't very useful as a communication method.

We did get it working, the details are in my last message.

At several points I had Ethereal going on the desktop, and tcpdump on 
the tun interface on the openvpn gateway and on the asterisk server.

Thanks for the help everyone.

Eric

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