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Cisco ASR 903 Router Hardware Installation Guide
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Chapter2 Preparing for Installation
Site Planning
The distance between the center lines of the mounting holes on the two mounting posts must be 18.31
inches ± 0.06 inch (46.50cm ± 0.15 cm). The rack-mounting hardware included with the chassis is
suitable for most 19-inch equipment racks.
Consider installing the CiscoA SR903 Router in a rack with the following features:
•Network Equipment Building System (NEBS) compliant, 19-inch (48.3 cm) wide rack.
•EIA or European Telecommunications Standards Institute (ETSI) hole patterns in the mounting
rails. The required mounting hardware is shipped with the CiscoASR 903 Router. If the rack that
you plan to install the system in has metric-threaded rails, you must provide your own
metric-mounting hardware.
•Perforated top and open bottom for ventilation to prevent overheating.
•Leveling feet for stability.
Note The Cisco ASR 903 Router should not be installed in an enclosed rack because the chassis requires an
unobstructed flow of cooling air to maintain acceptable operating temperatures for its internal
components. Installing the router in any type of enclosed rack—even with the side doors
removed—could disrupt the air flow, trap heat next to the chassis, and cause an overtemperature
condition inside the router. If you use an enclosed rack, ensure that there are air vents on all sides of the
rack and there is proper ventilation.
Equipment Rack Guidelines
The placement of the rack can affect personnel safety, system maintenance, and the system’s ability to
operate within the environmental characteristics described in the “System Specifications” section on
page 1-2. Choose a proper location for the Cisco ASR 903 Router by following the following guidelines.

Locating for Safety

If the Cisco ASR 903 Router is the heaviest or the only piece of equipment in the rack, consider
installing it at or near the bottom to ensure that the rack’s center of gravity is as low as possible.
For additional information about the proper placement of electronic equipment, consult the document
GR-63-CORE, Network Equipment Building System (NEBS) Requirements: Physical Protection.

Locating for Easy Maintenance

Keep at least 3 feet of clear space at the front and back of the rack. This space ensures that you can
remove the CiscoASR 903 Router components and perform routine maintenance and upgrades easily.
Avoid installing the CiscoASR 903 Router in a congested rack and consider how routing of cables from
other pieces of equipment in the same rack could affect access to the router cards.
The sides of the chassis must remain unobstructed to ensure adequate airflow and prevent overheating
inside the chassis.
Allow the following clearances for normal system maintenance:
•At the top of the chassis—At least 3 inches (7.6 cm)
•Sides of the chassis—3 to 4ft (91.44 cm to 121.92 cm)
To avoid problems during installation and ongoing operations, follow these general precautions when
you plan equipment locations and connections: