APC AP7900 Watchdog Features, Network interface watchdog mechanism, Resetting the network timer

Switched Rack PDU

USER’S GUIDE

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Watchdog Features

Overview

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 System: Warmstart event is recorded in the event log.

Network interface watchdog mechanism

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.

Resetting the network timer

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.

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