With IPHost Network Monitor you can run simple snmp requests against a Nortel device in your network.
x25DtePeerX25Address
x25 Dte Peer X25 Address
1.3.6.1.4.1.562.2.4.1.90.2.10.1.3
This attribute specifies the X.25 address that identifies the remote host with which this Peer component allows communication. The remote X.25 interface could be subdivided through the use of RemoteGroup components; in which case this x25Address is the X.25 address of the destination's RemoteGroup (not to be confused with the RemoteGroup indicated by the linkToRemoteGroup attribute of THIS Peer component).
Back to Nortel-Magellan-Passport-X25DteMIB MIB page.
IPHost Network monitor allows you to monitor x25DtePeerX25Address 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 multiplexers right now.