In an open-frame rack, center-mounting is generally preferable to front-mounting because the more even distribution of weight provides greater stability. If you center-mount the chassis, you use the center-mounting brackets attached to the chassis. If you front-mount the chassis, you use the front-mounting flanges, and must remove the center-mounting brackets.
Table 1 specifies the mounting holes in which you insert the mounting screws (an X indicates a mounting hole location), and cage nuts if needed. The hole distances are relative to one of the standard “U” divisions on the rack. For reference, the bottom of all mounting shelves is at 0.04 in. (0.02 U) above a “U” division.
Table 1: Open-Frame Rack Mounting Hole Locations
Hole | Distance Above “U” Division | Large Shelf | |
|---|---|---|---|
59 | 34.13 in. (86.7 cm) | 19.50 U | X |
53 | 30.63 in. (77.8 cm) | 17.50 U | X |
50 | 28.88 in. (73.3 cm) | 16.50 U | X |
44 | 25.38 in. (64.5 cm) | 14.50 U | X |
41 | 23.63 in. (60.0 cm) | 13.50 U | X |
35 | 20.13 in. (51.1 cm) | 11.50 U | X |
32 | 18.38 in. (46.7 cm) | 10.50 U | X |
31 | 17.75 in. (45.1 cm) | 10.14 U | X |
To install the large mounting shelf (see Figure 1) in an open-frame rack:
Figure 1: Installing the Mounting Hardware for an Open-Frame Rack

Before front-mounting the router in an open-frame rack, you must remove the center-mounting brackets from the chassis.
To remove the center-mounting brackets (see Figure 2):
Figure 2: Removing the Center-Mounting Bracket

The router is shipped with each spacer bar attached to the rear of each front-mounting flange. If you are installing the chassis in an open-frame rack, removing the spacer bars is optional.
To remove the spacer bars: