With IPHost Network Monitor you can run simple snmp requests against a Nortel device in your network.
vsrTotalFailedCallsFromIf
VoiceRoute Total Failed Calls From If
1.3.6.1.4.1.562.2.4.1.117.15.1.2
This attribute counts indicates the total number of calls that have been received by this VoiceSubroute from the PBX which failed to be successfully routed through the subnet for various reasons. The value wraps to zero when it reaches its maximum.
Back to Nortel-Magellan-Passport-VoiceNetworkingMIB MIB page.
IPHost Network monitor allows you to monitor vsrTotalFailedCallsFromIf on Allied Telesis device via the SNMP protocol. Download IPHost Network Monitor (500 monitors for 30 days, 50 monitors free forever) to start monitoring Nortel secure routers right now.