Cisco Catalyst 9600 Series Hardware Installation Manual page 60

Rack-Mounting the Chassis in NEBS-Compliant Mode
Figure 29: NEBS-Compliant Air Filter
Note
Step 8
Install the top and base covers as shown in the illustrations:
Cisco Catalyst 9600 Series Switches Hardware Installation Guide
56
We recommend that you change the air filter every 3 months. However, examine the air filter once
a month (or more often in dusty environments) and replace it if it appears to be excessively dirty
or damaged. To comply with Telecordia GR-63-Core standard air filter requirements for NEBS
deployments, the air filter must be replaced, not cleaned.
Installing the Switch