When you're using SNMP to poll a router for stats on a given interface sometimes you need to know the SNMP IfIndex ID of a given interface. It's easy (example from a 7206 running 12.4(9)T2):
router-1#show snmp mib ifmib ifindex atm1/0.1080 Interface = ATM1/0.1080, Ifindex = 190
router-1#show snmp mib ifmib ifindex detail atm1/0.1080 Description ifIndex Active Persistent --------------------------------------------------------------- ATM1/0.1080-aal5 layer 190 yes enabled