[kitonne]

I am on vacation, and my hotel is providing free wifi service. After a rough start and E39.95 for a new Linksys PCMCIA card with WPA2 support (they do not support WEP), I now have web access.

As soon as I had web, next thing on the agenda was, of course, to fire up XPro and try calling a couple of friends back home in Chicago, via FWD. A couple of frustrating minutes later, I discovered that STUN alone does not do the trick, and that I had to enable the voice proxy. OK, simple to fix, but voice was still very choppy, even with low bit rate codecs, and FTP transfers both ways clock at well over 200kbps, and I have zero lost ping packets. Next I fired up winstun, and tried a couple of times in a row to see what is going on with STUN and why does it not work as expected.

That is how I discovered that my hotel has TWO external IPs, one "restricted NAT, voice OK", and the second one "symmetric NAT, voice will not work".

Any suggestions of how to force my IP packets to use a given external IP port versus the other, given the fact that I have no access to the router, and the guys at the reception know absolutely nothing about this issue would be greatly appreciated. I understand what the router is trying to do, and load balancing is a great idea in general, but not for RTP packets,

My notebook runs XP SP2. Calling late at night (local time) did yeld some good quality calls - I guess that below a treshold, all packets go through only one of the external interfaces, and load balancing did not come into play, but other times, even with ILBC, the quality is too low for a conversation. Any suggestions of what to try out would be greatly appreciated....

[RobT]

I usually recommend IAX rather than SIP in such situations for exactly this reason. In a hotel, you have no control over the NAT layering, port forwarding etc. IAX will work in many situations where SIP won't. (Not all providers allow IAX connections, but FWD does.)

If you want to stick with SIP, then you're going to have to configure XP's routing table to send the UDP packets via the first external address. (Sorry, I don't know how to do that under Windows, but I'm sure Google does.)