Cisco Systems Cisco 12816 Manuale Utente

The router chassis can be installed in either a front-mounted position or a 
center-mounted position.

In a front-mounted position, the chassis rack-mounting flanges are secured 
directly to the rack posts.

In a center-mounted position, an optional set of center-mount brackets are 
secured to the rack posts and the chassis rack-mounting flanges are then 
secured to the center-mount brackets. The center-mounted position moves the 
center of gravity of the chassis closer to the vertical axis of the rack posts, 
which adds to the security and stability of the rack installation.

Before you install the chassis, measure the space between the vertical mounting 
flanges (rails) on your equipment rack to verify that the rack conforms to the 
measurements shown in 

Mark and measure the distance between two holes on the left and right mounting 
rails.

The distance should measure 18.31 inches ± 0.06 inches (46.5 cm ± 0.15 cm).

Measure for pairs of holes near the bottom, middle and top of the 
equipment rack to ensure that the rack posts are parallel.

Measure the space between the inner edges of the left front and right front 
mounting flanges on the equipment rack. 

The space must be at least 17.7 inches (45 cm) to accommodate the chassis 
which is 17.25 inches (43.8 cm) wide and fits between the mounting posts on 
the rack.