[Serusers] Broken "SIP Aware" Router

[Andres]

We have started having problems with customers in BellSouths ADSL 
network.  New customers are being given the Westell ADSL modem which 
appears to be "SIP Aware".  But the implementation is terribly broken.

The symptoms are that SIP INVITES cannot penetrate the NAT on the Modem 
even though we have a permanent Keep-Alive from the inside (every 15 
seconds).  Furthermore when the customer tries to make a call, the modem 
changes the source port of every single packet of the dialog.  Thus 
breaking the SIP dialog completely.

Our interim solution was to setup these customer on an alternate server 
listening on a different port. 

For everybody's reference the modem version is:  Westell B9061003006 and 
the Software is: 03.00.61

I have tried to contact Westell directly but they have not answered.  I 
hope this is not something thats going to start happening with all modem 
manufacturers or else were going to have loads of trouble.


-- 
Andres
Network Admin
http://www.telesip.net