Recently I needed to check traffic on specific interfaces of a Cisco 3845 Router. I didn't have a MIB file uploaded to our SNMP workstation, and descriptions of measures were not in synch with the router. Thus I needed to figure out which interface was which. There were 8 valid instances of interface metrics on the router. I was interested in BitsIn/Sec, BitsOut/Sec, and IntSpeed. From IntSpeed, I got the following numbers:
1. 1,000,000,000
2. 1,000,000,000
3. 4,294,967,295
4. 44,736,000
5. 45,000,000
6. 44,736,000
7. 45,000,000
8. 4,294,967,295
Thus I figured out that Serial 0 is 5 and serial 1 is 7. Gig 0 and Gig 1 are 1 and 2. We have two DS-3 circuits (ATT calls them DNECs) in. SNMP may be wonderful but MIBs are a pain. I thought I would write this down before I erase my whiteboard with tomorrow's problem and solution. You can find Cisco's guide to it's MIB and SNMP here.