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Posted by Wolfgang S. Rupprecht on May 2, 2007, 10:27 am
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beheer@netbasics.nl writes:
>> Well my first guess would be that work doesn't know how to route to
>> 192.168.21.4. Can you ping that address from the phone (or a computer
>> that is put on the same network as the phone)?
>
> All computers and ip phones at work have 192.168.1.1 as default
> gateway. On the default gateway I've made a static route
> (192.168.21.4/255.255.255.255 to 192.168.1.32 on the LAN interface)
Sounds ok, so far.
> I can't ping my phone from work. I tried to ping directly from the
> gateway to my phone. Also doesn't work.
> I tried a packet sniffer on my computer. I don't see any packets when
> pinging. I suspect Windows is blocking because I think it's like
> trying to reach a local computer directly from the internet.
Ah, I didn't realize you are NAT-ing the phone? I don't know anything
about MS software, but isn't there some way to turn off the NAT? You
really don't need it or want it. Straight routing would remove quite
a lot of issues.
> - when my phone is used, the call manager server should act as a proxy
> (I can't find any settings to do that)
> - my phone is known to the call manager server as 192.168.21.4. If I
> could somehow translate the return packets to 192.168.1.32, then I
> think it would work. I would forward the packets coming in on
> 192.168.1.32 to 192.168.21.4
> - do some kind of NAT on my computer so that my phone identifies
> itself as 192.168.1.32
NAT-ing voip's SIP (control) and RTP (voice data) packets requires
more work in the NAT than just slapping a new IP address in the IP
header. There are copies of the IP address in the data part of the
SIP packet that needs to be translated too. NAT can be made to work,
but only if you have the right kind of NAT and some external help from
a STUN server. If you can turn off the NAT you save yourself a world
of hurt.
> All looks complicated, if feasible at all.
When you hit a brick wall, walk around it. ;-) Change the rules of
the game.
-wolfgang
--
Wolfgang S. Rupprecht http://www.wsrcc.com/wolfgang/
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