[cisco-voip] H323 Call Preservation added in 12.4(9)T

[Robert Kulagowski]

We have it configured and (unfortunately) use it.  Calls stay up during 
transition in and out of SRST mode.

If you're in "normal" mode and you go into SRST, your call stays active, 
but your phone won't register into SRST mode until after you hang up. 
At that point it does its little reset dance and registers with the CM.

Same thing coming out of SRST mode; if you're on an active call and the 
WAN becomes available, your phone stays on the call until you hang up, 
at which point it will come out of SRST.

Also, calls will stay up through a transition in and out of SRST mode if 
you're on a long call.

NOTE:  Don't install 12.4.9(T)!  We discovered a bug 
(http://www.cisco.com/cgi-bin/bugtool/onebug.pl?bugid=CSCsf21458) that 
causes the phones to continuously deregister each other; TAC cut us a 
custom IOS (12.4.9T build 134) which is what we're using, but you don't 
need to go through that hassle:

First Fixed-in Version  	 12.4(11.1)T, 12.4(9)T02, 12.4(4)XC05