I posted a short while back on this topic for older versions of Communications Manager. Ā Leave it to Cisco to move things around and make me do it again. Ā :)
So here’s where you find the option :
Go to Device -> Device Settings -> SIP Profile. Ā Select the profile you want to edit (If you use the default profile, you will need to make a copy of it).
Scroll down to the bottom section (Trunk Specific Configuration)Ā and find the SIP Rel1XX Options parameter. Ā Change it to Send PRACK if 1xx Contains SDP.
As I mentioned in the other post, this parameter tells the Communications Manager to send ACK packets back in response to 100 series SIP message received that contains an SDP section.
Press theĀ SaveĀ button and you’re done.
If you had to copy the SIP Profile, you will now need to apply the profile to your SIP trunk, then reset it to apply the changes.
Remember! Resetting the SIP Trunk will DROP all active calls.
Good luck!