Add this to your mrtg.cfg File:
#--------------------------------------------------------
Target[HOSTNAME_PASSPORT.cpu]: 1.3.6.1.4.1.2272.1.1.20.0&1.3.6.1.4.1.2272.1.1.20.0:SNMP_COMMUNITY@HOSTNAME_PASSPORT
MaxBytes[HOSTNAME_PASSPORT.cpu]: 100
Unscaled[HOSTNAME_PASSPORT.cpu]: ymwd
Options[HOSTNAME_PASSPORT.cpu]: nopercent, unknaszero, gauge
YLegend[HOSTNAME_PASSPORT.cpu]: Prozent
XSize[HOSTNAME_PASSPORT.cpu]:300
YSize[HOSTNAME_PASSPORT.cpu]:100
Title[HOSTNAME_PASSPORT.cpu]: HOSTNAME_PASSPORT#CPU Slot 5 Auslastung
PageTop[HOSTNAME_PASSPORT.cpu]: <H1>CPU Auslastung HOSTNAME_PASSPORT#5</H1>
#---------------------------------------------------------
If you don't know the MIB-OIDs (for CPU utilization for example) it's always a good trick to use the Nortel Device Manager to get the required value and let a sniffer programm capture the SNMP Packets.