Monitoring performance on Ethernet interfaces comes down to monitoring bandwidth utilization using the methods described in Chapter 12, “Monitoring System Interfaces.”
The following MIB objects (from RFC 2233) are the most useful in measuring the amount of traffic flowing across Ethernet interfaces:
ifInOctets, ifOutOctets The number of octets transmitted or received on a given interface.
ifHCInOctets, ifHCOutOctets The number of octets transmitted or received on a given high-speed interface (but support does not start until OS 12.0 or Catalyst switch OS 3.1).
ifInUcastPkts, ifOutUcastPkts The number of unicast packets transmitted or received on a given interface.
ifInNUcastPkts, ifOutNUcastPkts ...