Cisco Emergency Responder needs to be able to make a Simple Network Management Protocol (SNMP) connection to the Cisco CallManager. If there are any connectivity issues between the two applications, it can cause discovery of the phones to fail.
To resolve this issue, try to ping the Cisco CallManager server from the Cisco Emergency Responder.
Once you can ping the Cisco CallManager, make sure the SNMP settings are correct on the CallManager.
Perform these steps:
Open the services on Cisco CallManager.
Go to Start > Settings > Control Panel > Administrative Tools >Services Properties > SNMP > Properties > Security Tab.
Make sure the community string is set to read-only access.
Note: Verify that the community string setting is read-only on all the Cisco CallManagers in the cluster.
Check that the radio button for Cisco Emergency Responder host readability is selected.
If the Accept SNMP packets from these hosts radio button has been selected, make sure the IP addresses of the master and backup Cisco Emergency Responder servers are visible in the bottom window.
For more information about resolving Cisco Emergency Responder, refer to these documents: