asterisk users - Sep 2009 - Problem with Cisco 7911G and ABE 2.1.2C - randomly cannot DIAL

Guys,
I assure you this is probably the most interesting and weird problem you
have encountered (or definitely up there). I'm using ABE 2.1.2C and
roughly 500 or so Cisco 7911G Phones. 

The following is what happens:

When trying to dial a number from the cisco 7911G phone it may randomly
get stuck on 'Dialing'. The SIP history on the asterisk end goes like
this:

1. Cisco -> INVITE -> Asterisk
2. Asterisk -> Proxy Authorization Required -> Cisco
3. Cisco -> gone to sleep.

If I login to the cisco phone, (using log/log) i can see that the phone
is trying constantly to reach the asterisk server. It retransmits the
packet 10 times and then gives up and the call terminates.

This behavior depends primarily on the length of the number dialed,
though sometimes the 'mood' of the Cisco also comes into play. It may be
impossible to dial 11 digit numbers at one point but 2 hours later it
may magically work.

All other phones on this network work perfectly. This includes Linksys,
polycom and Grandstream. The most expensive phone causes issues - go
figure! :)

The following alleviates the problem:

1. If I mess around with the length of the 'realm' parameter in sip.conf
it can randomly make the phones happy or unhappy. The smaller the
better, however some phones may still get stuck on dialing.

2. Removing secrets from the sip.conf friend entry fixes this issue. Its
the proxy authorization message that really pisses the cisco off. 

4. I have tried randomly to use insecure, fromdomain, etc but nothing
works. 

Also- the same phones work perfectly with our Asterisk 1.4.26 office
server.

Help is most appreciated. We are at a loss here. 


-- 
Faraz R Khan
CEO
Emergen Consulting Pvt Ltd
www.emergen.biz
+92.21.529.0381 (3 lines) x200