APC AP7900 Manual Do Utilizador

To detect internal problems and recover from unanticipated inputs, the Rack 
PDU uses internal, system-wide watchdog mechanisms. When it restarts 
itself to recover from an internal problem, a 

 event is 

recorded in the event log.

The Rack PDU implements internal watchdog mechanisms to protect itself 
from becoming inaccessible over the network. For example, if the Rack 
PDU does not receive any network traffic for 9.5 minutes (either direct 
traffic, such as SNMP, or broadcast traffic, such as an Address Resolution 
Protocol [ARP] request), it assumes that there is a problem with its network 
interface and restarts itself.

To ensure that the Rack PDU does not restart if the network is quiet for 9.5 
minutes, the Rack PDU attempts to contact the Default Gateway every 4.5 
minutes. If the gateway is present, it responds to the Rack PDU, and that 
response restarts the 9.5-minute timer. If your application does not require 
or have a gateway, specify the IP address of a computer that is running on 
the network most of the time and is on the same subnet. The network traffic 
of that computer will restart the 9.5-minute timer frequently enough to 
prevent the Rack PDU from restarting.