Cisco Emergency Responder (CER) uses SNMP to gather information from switches that IP phones are connected to. In my experience, this process is slow, fragile, and error-prone. I know of several bugs related to this process regarding crypto and IPv6.
Suggestion: Leverage phone registrations, which is a distributed push of information into CUCM.
Details:
Phones would include their CDP information as part of their registration with CUCM. This would include the neighbor switch and switch port.
CER would query CUCM for phone registrations, which would include the new information described above.
CER would link the defined switches, their ports, and ERLs with the phone neighbor details, avoiding SNMP scans.
