http://www.cisco.com/c/en/us/td/docs/net_mgmt/prime/infrastructure/3-0/user/guide/pi_ug/mon-pol-thresh.html#pgfId-1090868
(presumably the same procedures apply to 3.1)
M.
-- ' 'Good body every evening' ' this sentence was once spotted on a logo at the entrance of a Weight Watchers Club !