Linux – Monitor ethernet traffic of windows host using check_snmp with nagios

I currently have nagios ver. 3.3.1 running on CentOS 5.6. All of my windows hosts are being monitored using check_nt with nsclient++ and it is working perfectly.

What I would like to do is monitor network traffic of these windows hosts using check_snmp. I have setup up SNMP correctly and I am all to do a full snmpwalk from the nagios host.

I know very little about SNMP and I am not sure what OID's are actually the ethernet device of the windows host. When I do a full snmpwalk snmpwalk -c community -v 2c host -m ALL .1 I get an overwhelming amount of data.

My question is how do I figure out which OID's are my window's host ehternet interfaces? Also is there a list or tutorial on understanding SNMP? I have looked all over and have not been able to find any that are beginner friendly.

Edit:

I found and tried the following command snmpwalk -v 2c -c community host $DEVICE NAME$ .1.3.6.1.2.1.31.1.1.1.1 and the output was as follows:

IF-MIB::ifName.1 = STRING: loopback_0
IF-MIB::ifName.2 = STRING: tunnel_0
IF-MIB::ifName.3 = STRING: tunnel_1
IF-MIB::ifName.4 = STRING: tunnel_2
IF-MIB::ifName.5 = STRING: tunnel_3
IF-MIB::ifName.6 = STRING: ppp_0
IF-MIB::ifName.7 = STRING: ethernet_0
IF-MIB::ifName.8 = STRING: ethernet_1
IF-MIB::ifName.9 = STRING: ethernet_6
IF-MIB::ifName.10 = STRING: ppp_1
IF-MIB::ifName.11 = STRING: ethernet_5
IF-MIB::ifName.12 = STRING: tunnel_4
IF-MIB::ifName.13 = STRING: tunnel_5
IF-MIB::ifName.14 = STRING: ethernet_2
IF-MIB::ifName.15 = STRING: ethernet_3
IF-MIB::ifName.16 = STRING: ethernet_4
IF-MIB::ifName.17 = STRING: ethernet_7
IF-MIB::ifName.18 = STRING: ethernet_8

so from here I am not sure which Ethernet device is the correct one or what other OID's I could use to monitor bandwidth on this host.