I'm trying to find SNMP OID (and MIB in which OID contain) to monitor L2 of ISDN PRI line.
I've configured Nagios check for interface, but even serial 0/x/0:15 is up/up, that doesn't mean its working on L2.
What I need is to distinguish between states: L1/L2 DOWN, L1 ACTIVE and L2 DOWN or L2 TEI_ASSIGNED or L2 MULTIPLE_FRAME_ESTABLISHED - working line on L2.
Can you please point me to right way or OID/MIB?
I've found several discussions but any of them doesn't solving similar issue.
Thank you in advance,