APC ACRD501, ACRP501, ACRP500, ACRP100, ACRP101, ACRD500 Display Interface LEDs, Watchdog Features

Display Interface LEDs

Status

This LED indicates the status of the cooling unit.

Check log

When yellow, this LED indicates that at least one new critical alarm, warning alarm, or event has occurred since the last time the event log was viewed from the display interface.

Warning alarm

When yellow, this LED indicates that a warning alarm condition exists and may require your attention to prevent it from deteriorating into a critical state. A new alarm will cause a beep every 30 seconds until you silence the alarm by pressing any function key.

Critical alarm

When red, this LED indicates that a critical alarm condition exists and requires your immediate attention. An audible alarm beeps every 30 seconds. Press any function key to silence the audible alarm.

Watchdog Features

Overview

To detect internal problems and recover from unanticipated inputs, the cooling unit uses internal, system- wide watchdog mechanisms. When it reboots to recover from an internal problem, a System: Warmstart event is recorded in the event log.

Network interface watchdog mechanism

The cooling unit implements internal watchdog mechanisms to protect itself from becoming inaccessible over the network. For example, if the cooling unit 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.

Resetting the network timer

To ensure that the cooling unit does not restart if the network is quiet for 9.5 minutes, the cooling unit attempts to contact the Default Gateway every 4.5 minutes. If the gateway is present, it responds to the cooling unit, 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 reset the 9.5-minute timer frequently enough to prevent the cooling unit from restarting.