Select a Bay Networks/Nortel Accelar or Ethernet Routing Switch (ERS) chassis switch as the target host to create a monitor — the SNMP service should be up and running on it. Click New Monitor, then check SNMP Custom on the Favorites tab, click Next, and confirm the host. On the next page, click Select... to open the built-in SNMP MIB Browser and type rcSysBufferUtilPeak into the Find box to locate it in the OID tree, then select it and click OK. It reports the largest buffer utilization observed since the system last booted, as a percentage. On the monitor's Main parameters page you can set the target's SNMP port (default 161), credentials, polling interval, and other settings — see the SNMP Monitor help for details. On the State conditions and Alerting tabs, configure when the monitor should change state and trigger an alert; since this is an INTEGER-type OID, Value bounds is the most useful condition here — trigger an alert if the peak reaches 90% or higher, since a high historical peak indicates the system came close to exhausting its packet buffers at some point. Click Finish to create the monitor; you can adjust any parameter later.