With IPHost Network Monitor you can run simple snmp requests against a Cisco device in your network.
ccmeEphonePrimaryDn
Cisco Call Manager Express Ephone Primary Dn
1.3.6.1.4.1.9.9.439.1.1.43.1.18
This object indicates the primary extension DN (Ephone-Dn) for this Cisco IP phone. Zero value indicates no primary extension DN is set for this IP phone
Back to CISCO-CCME-MIB MIB page.
IPHost Network monitor allows you to monitor ccmeEphonePrimaryDn on Cisco device via the SNMP protocol. Download IPHost Network Monitor (500 monitors for 30 days, 50 monitors free forever) to start monitoring Cisco routers right now.