The PS/PSII both have Post-diagnostic testing for hardware verification, you can monitor ports and ethernet activity from the front panel. Both can be SNMP managed, network statistics gathered. The PSII has the set trace utility for debugging things such as PPP, serial, ICMP, etc. The PSII also supports RADIUS.

NOTE for users of Front Panel Diagnostics
Some terminals require DCD to be high or floating in order to initiate communication. Use of a fully pinned out cable which wires anything from the PortServer (or PSII) to DCD will initially tie this signal low and may prevent the terminal from communicating. In this case, use of a 3 wire cable which only connects Tx, Rx, and SG is recommended.