CTI Port is used for the Onsite Alert. The 911 call and 913 callback call flows don't involve a CTI Port - they use CTI Route Points.
The number of telephony ports (CTI Ports) that you have assigned on CER will determine the number of simultaneous onsite alerts that can be notified of an emergency call.
CER > Phone Tracking > Cisco Unified Communications Manager Clusters > Telephony Port Begin Address and Number of Telephony Ports
On CUCM,
- the CTI Port DNs should correpond with the CER configuration (contiguous set of numbers)
- Ensure that the CTI Ports are added in the controlled list of devices for the CER Application User config page on CUCM
- CTI Port DN CSS + Device CSS should have access to the partitions of the onsite alerts' phones.
- Sriram
