You must find out the instance ID of the interface before you can monitor it. To do so, you can use either a GUI or command line tool.
You can use the SnmpB program.
First, open the Modules tab, make sure the IF-MIB module is loaded.
Then, Walk the ifDescr OID to list all interface instances:
In the above screen shot, the instance ID of the Intel(R) PRO/1000 MT Network card is 10.
Use the snmpwalk command to find out the instance ID:
snmpwalk -Oa -c public -v 1 ntserver.example.com IF-MIB::ifDescr
Output:
RFC1213-MIB::ifDescr.1 = STRING: "Software Loopback Interface 1."
RFC1213-MIB::ifDescr.2 = STRING: "WAN Miniport (SSTP)."
RFC1213-MIB::ifDescr.3 = STRING: "WAN Miniport (L2TP)."
RFC1213-MIB::ifDescr.4 = STRING: "WAN Miniport (PPTP)."
RFC1213-MIB::ifDescr.5 = STRING: "WAN Miniport (PPPOE)."
RFC1213-MIB::ifDescr.6 = STRING: "WAN Miniport (IPv6)."
RFC1213-MIB::ifDescr.7 = STRING: "WAN Miniport (Network Monitor)."
RFC1213-MIB::ifDescr.8 = STRING: "WAN Miniport (IP)."
RFC1213-MIB::ifDescr.9 = STRING: "RAS Async Adapter."
RFC1213-MIB::ifDescr.10 = STRING: "Intel(R) PRO/1000 MT Network Connection."
RFC1213-MIB::ifDescr.11 = STRING: "vmxnet3 Ethernet Adapter."
RFC1213-MIB::ifDescr.12 = STRING: "isatap.{4A5DB7E5-629D-4801-9CCE-0CED57472D5E}."
RFC1213-MIB::ifDescr.13 = STRING: "WAN Miniport (IPv6)-QoS Packet Scheduler-0000."
RFC1213-MIB::ifDescr.14 = STRING: "WAN Miniport (IP)-QoS Packet Scheduler-0000."
RFC1213-MIB::ifDescr.15 = STRING: "WAN Miniport (Network Monitor)-QoS Packet Scheduler-0000."
RFC1213-MIB::ifDescr.16 = STRING: "vmxnet3 Ethernet Adapter-QoS Packet Scheduler-0000."
Now you know the instance ID of the Intel LAN card is 10, you can read IN/OUT octets by:
#IN: snmpget -c public -v 2c ntserver.example.com .1.3.6.1.2.1.2.2.1.10.65539 #OUT: snmpget -c public -v 2c ntserver.example.com .1.3.6.1.2.1.2.2.1.16.65539
The numeric OID above can be found by snmptranslate:
snmptranslate -On IF-MIB::ifInOctets snmptranslate -On IF-MIB::ifOutOctets