APC Switched Rack Power Distribution Unit (PDU) - Manual (Page 16)

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USER
’S GUIDE
switched rack pdu
12
Watchdog Features
Overview
To detect internal problems and recover from unanticipated inputs, the PDU
uses internal, system-wide watchdog mechanisms. When it restarts itself to
recover from an internal problem, a System: Warmstart event is recorded
in the Event Log.
Network interface watchdog mechanism
The PDU implements internal watchdog mechanisms to protect itself from
becoming inaccessible over the network. For example, if the 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.
Resetting the network timer
To ensure that the PDU does not restart if the network is quiet for 9.5
minutes, the PDU attempts to contact the Default Gateway every 4.5
minutes. If the gateway is present, it responds to the 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 PDU from restarting.