The users on one of my remote sites reported they experienced five seconds of delay when transfer calls. It is a Cisco Communication Manager system, on Cisco phones and skinny protocol. The CM is on the data center, the WAN connection is an IPSEC VPN between an ISR on the remote site and a Cisco ASA in the data center. When the delay happened, Cisco Phone would display “UCM down, features disabled” message.
It turns out that the lost of communication between Cisco phone and the CM was due to the ISR CBAC skinny inspection. As soon as I turned off the skinny inspection (no inspect skinny), the issue disappeared.
The IOS version was 12.4(21a). I didn’t have the time to check cisco.com for any reported bug. So if you ran into this issue, remote skinny inspection and give it a try.
asa,
Firewall,
isr,
Voice
Cisco,
Voice and Video
