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Hardware Installation Guide for the Cisco 4451-X Integrated Services Router
OL-27644-01
Chapter 1 Overview of the Cisco 4451-X Integrated Services Router
About Slots and Interfaces
Fans, Ventilation, and Airflow
Chassis Ventilation
An internal fan tray consisting of 4 fans provides chassis cooling. An onboard temperature sensor
controls the fan speed. The fans are always on when the router is powered on. Under most conditions,
the fans operate at the slowest speed to conserve power and reduce fan noise. The fans operate at the
higher speeds when necessary under conditions of higher ambient temperature. To replace a fan tray, see
the “Replacing a Fan Tray” section on page 6-34.
• Figure 1-8 shows the Cisco ISR 4451-X airflow.
Figure 1-8 Cisco ISR 4451-X Airflow)
About Slots and Interfaces
This section covers the following topics:
• About Slot, Subslot (Bay), and Port Numbering, page 1-17
• Slot Numbering, page 1-19
• Subslot/Bay Numbering, page 1-20
• Gigabit Ethernet Management, page 1-20
• About Fixed Interfaces, page 1-20
About Slot, Subslot (Bay), and Port Numbering
The Cisco ISR 4451-X supports two types of interface modules: Enhanced Service Modules (SMs) and
Network Modules (NIMs).
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