Environmental characteristics in Cisco devices involve data points such as temperature, voltages, and fan statuses. There is no compelling reason to proactively track any of this kind of data to determine the performance of your Cisco device, so we will focus only on fault management for these environmental characteristics. If you do want to get these data points, you can retrieve them on demand with SNMP queries or show commands. The router can also notify the network management station via SNMP traps of thresholds being exceeded.
Most of the environmental factors that can be monitored reside in the core Cisco devices, such as the 7xxx series routers or the 5xxx series Catalyst switches. Most of the low-end routers and switches do not display or report the environmental characteristics, except for the 3600 series routers. Because of the variable nature and constant fluctuation of environmental data, SNMP traps are the main source of identifying environmental problems. That is, you'll let the device tell the network Management Station (NMS) when a problem occurs. (The ENVMON SNMP trap is discussed later in this chapter.)
In the 7500 series routers, the chassis interface controls the environmental monitoring and reporting functions. The monitoring functions constantly monitor the internal chassis air temperature and DC voltage and currents.
Each power supply monitors its own voltage and temperature, and shuts itself down if it detects a critical condition within the power supply. If conditions reach Shutdown thresholds, the system shuts down to avoid equipment damage from excessive heat. There are also Warning and normal condition thresholds reported prior to Shutdown state. In addition to temperature and voltage monitoring, the router also monitors the fan and blower in the chassis. SNMP trap notifications, console log messages, or syslog messages are reported when certain thresholds are reached and exceeded relating to these characteristics.
For the Catalyst series switches, there are three levels of status conditions relating to environmental characteristics:
When alarm conditions are met on the switch, SNMP traps and log messages, syslog and console, are reported, indicating the threshold-exceeded condition.