The rack model represents a physical two- or four-post equipment rack in which [devices](./device.md) can be installed. Each rack must be assigned to a [site](./site.md), and may optionally be assigned to a [location](./location.md) within that site. Racks can also be organized by user-defined functional roles. The name and facility ID of each rack within a location must be unique.
Rack height is measured in *rack units* (U); racks are commonly between 42U and 48U tall, but NetBox allows you to define racks of arbitrary height. A toggle is provided to indicate whether rack units are in ascending (from the ground up) or descending order.
Each rack is assigned a name and (optionally) a separate facility ID. This is helpful when leasing space in a data center your organization does not own: The facility will often assign a seemingly arbitrary ID to a rack (for example, "M204.313") whereas internally you refer to is simply as "R113." A unique serial number and asset tag may also be associated with each rack.
Additional statuses may be defined by setting `Rack.status` under the [`FIELD_CHOICES`](../../configuration/data-validation.md#field_choices) configuration parameter.
### Role
The functional [role](./rackrole.md) fulfilled by the rack.
### Facility ID
An alternative identifier assigned to the rack e.g. by the facility operator. This is helpful for tracking datacenter rack designations in a colocation facility.
### Serial Number
The unique physical serial number assigned to this rack.
### Asset Tag
A unique, locally-administered label used to identify hardware resources.
Some additional fields pertaining to physical attributes such as height and weight can also be defined on each rack, but should generally be defined instead on the [rack type](./racktype.md).
