I need some assistance for caller ID associated to 911 dialing.
We have CUCM 11.5(1) and use CER for 911 dialing. All phones have an external phone number mask assigned. Same config that's been in place for many years, but just found an issue for outbound calls to the PSAP for 911 calls. Calls are correctly routing as follows: Phone > CUCM > CER > CUCM > SIPTrunk > CUBE > PSTN. Calls retrieve the appropriate ERL/ELIN info from CER, and come back to CUCM, hitting the route pattern associated with the ERL (calling party transformation mask set to the ELIN DID number). All of this is standard CER setup.
The problem comes when the call exits CUCM towards CUBE via our SIP trunk. The now-associated ELIN DID is overridden by the SIP trunk changing it back to the originating phone's external phone number mask, so when CUBE sees the call the SIP INVITE shows as the external phone number mask, which is what the PSAP receives also.
I've attached some config examples. All traces via CUCM show the call with the ELIN defined (as seen in attached RTMT snip). Everything traced at CUBE shows the ExtPhone#Mask (as seen in attached SIP_Invite_header Snip).
Our SIP Trunk has the Outbound Calls section > Caller Information box set at Caller ID DN: XXXXXXXXXX, and "Maintain Original Caller ID DN and Caller Name in Identity Headers" checked.
=== We've tried blanking out the DN field and unchecking the box on the SIP trunk, resetting the trunk, but have the same result for 911 calls, still shows the external phone number mask.
=== We've also tried to remove the checkmark at the ELIN route pattern for "Use calling party's external phone number mask", but also have the same result of external phone number mask seen.
We want the external phone number mask showing for all outbound calls EXCEPT those going to 911, which of course should reflect the ELIN DID.
Does anyone have any ideas on how to resolve this? I'd appreciate any help.
And, Happy Tranksgiving for those celebrating it this week.
