We’re currently upgrading from Asterisk 1.4 to Asterisk 11 and in the meantime we’re running two servers. A Cisco 7960 that is able to register against 1.4 is completely ignored by Asterisk 11, and yet other devices (e.g. a Cisco 7940) is able to register against Asterisk 11 no problems.
http://i.imgur.com/y94hkcT.png is a packet capture of the successful register from the 7940 on the left, and the unsuccessful register from the 7960 on the right, against the same server.
Asterisk “sees” the ignored register attempt (it shows up in sip debug), but does not give any error, or respond to the register in any way, it just silently drops the packet!
The only differences I can see between the two register’s is that the one that doesn’t work uses a different syntax in the “to” and “from” fields, as one surrounds the to and from in angled brackets <> and adds other info like tag, and includes some extra parameters like max-forwards and date, but why would Asterisk 11 ignore that packet because of those missing tags - especially since it works fine in Asterisk 1.4.