Phone calls random failing to connect at remote locations - Cisco Call Manager

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Phone calls random failing to connect at remote locations - Cisco Call Manager

L1 Bithead

We are in the process of converting over to Palo Alto firewalls at our remote locations from ASA firewalls. A few of our sites now are having some strange issues when attempting to make phone calls.We are a Cisco call manager shop.


Here is a basic setup of our network:

Remote Office <-Site to site VPN tunnell-> Main Office


Voice setup between those locations:

Analog lines (connected to router) - Remote Router - Remote Palo Alto <-Site to site VPN tunnell-> Main Office ASA firewall - Main Office Call-Manager


When someone at the remote location dials a external number, the phones SOMETIMES rings busy, even when the external phone number is not actually busy (tested and verified). The call will go through to the remote number but when they answer all they get is dead air. SOMETIMES the call goes through just fine. SOMETIMES when the call works and when the external number hangs up first the call stays active on the remote office's desk phone.


We've tried turning off ALG inside the SIP application, but when we test locally by setting up the calling search space to the remote office at a main office phone where we work, we still have problems.


Thank you for sharing our solution. 


we made the changes last week because all of our branch offices started having the same behavior with our SIP phones.


Now all the SIP phones are working fine. we can dial out and call between our extension. seems weird that after upgrading to 9.0 we started seen this issue and with 8.1 they worked fine.


Again Thank you for helping me.


I really appreciate your help. 



Thank you, this also solved the problem for our network as well.  Moving away from an MPLS to a VPN and calls couldn't exit the remote site.  Calls to the remote site worked fine.  Changing to UDP worked great.

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