Help : Getting Started : XRMon

Hewlett-Packard Extended RMON (XRMON) devices are discovered and configured using SNMP. You should make sure that your switches are configured to allow the Traffic Server SNMP read/write access and that the community string is set correctly in the Traffic Server configuration file.

Make sure you enable discovery in the configuration file:

[enterprise]
.
.
samplingEnabled = YES  ; turn on sampling on all devices
discoveryEnabled = YES ; sweep subnets for Extended RMON devices

You should also make sure that you add [zone] and [subnet] sections for all the address ranges that you would like tested for XRMON agents.