Outside calls to CMS

[VinnyC]

I am having an issue with incoming calls to out CMS and hoping someone can point me in the right direction.

When outside calls come into our CMS, they only see a black screen with no audio.  They should be prompted to enter a pin.  For our unpinned rooms, customers see the Cisco splash page with no audio.  

Outside calls to our CUCM is good.  

Internal calls to our CMS are good, including from remote sites on our network.  

Our network engineer says that our CMS is sending RTCP info through a port range in the 13,000's; however, the firewall is set to not allow anything below 16,000.  Prior to this issue, our CMS was using ports in the 40,000's; no changes were made. 

Where can I go to see what port(s) are being used for RTCP, and how can I change it?  I use CMM/CMS 3.4, vSphere 7, and CUCM 12.5.

Any assistance is greatly appreciated.  Thank you in advance!

[Mohammadreza Hadi]

did you check "MTP" option in your "SIP Trunk" between CUCM and CMS ?..

if it is un-checked, make it checked and reset the trunk and then test again,

it it is checked, make it un-checked, then reset, see what happens?..

[b.winter]

@VinnyC Could explain what you mean by "outside calls" exactly? Are these calls normal PSTN calls or do the come in via Expressway B2B? Could you explain your infrastructure setup a little bit more?