Chassis Ventilation; Real Time Clock - Cisco 2821 - Integrated Services Router Unified Communications Bundle Overview

Hardware Features

Chassis Ventilation

Internal multispeed fans provide chassis cooling, controlled by an onboard temperature sensor.
The Cisco 2801 router has two fans. The Cisco 2801 router with inline power includes two additional
fans integrated with the inline power supply, for a total of four fans. The Cisco 2801 internal fans operate
at three different speeds, running at the slower speeds to conserve power and reduce fan noise at ambient
temperatures below 40
The Cisco 2811 router has three fans that operate at a slower speed to conserve power and reduce fan
noise at ambient temperatures below 32
o
32 C.
The Cisco 2821 and Cisco 2851 routers have three fans that operate at a slower speed to conserve power
and reduce fan noise at ambient temperatures below 40
temperatures above 40
Ensure the device is not installed in close proximity to other devices which could lead to excessive
Caution
pre-heating of air at the air intake of the router.
Your chassis installation must allow unrestricted airflow for chassis cooling.
Caution
Cisco 2800 Series Router Installation and Preventive Maintenance
Periodic inspection and cleaning of the external surface of the router is recommended to minimize the
negative impact of environmental dust or debris on the router performance. The frequency of inspection
and cleaning is dependent upon the severity of the environmental conditions. Cleaning involves
vacuuming of router air intake and exhaust vents.
Caution Fans are dynamic Electro-Mechanical devices. As such, fans can fail for various electronic reasons, and
will eventually fail due to mechanical wear-out. Sites with ambient temperatures consistently above 25
degree C and with potentially high levels of dust or debris may require fan servicing.
Real-Time Clock
An internal real-time clock with battery backup provides the system software with time of day on system
power up. This allows the system to verify the validity of the certification authority (CA) certificate. In
the Cisco 2811, Cisco 2821, and Cisco 2851 routers, the clock and battery are permanently installed; the
battery lasts the life of the router under the operating environmental conditions specified for the router.
The Cisco 2801 router has a socketed lithium battery. This battery lasts the life of the router under the
operating environmental conditions specified for the router, and is not field-replaceable.
If the lithium battery in a Cisco 2801 router should fail, the router must be returned to Cisco for repair.
Note
Although the battery is not intended to be field-replaceable, the following warning must be heeded:
Overview of Cisco 2800 Series Routers
10
o
C. They operate at the highest speed in ambient temperatures above 40
o
C. They operate at high speed in ambient temperatures above
o
C.
o
C. They operate at high speed in ambient
o
C.
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