Each circuit may have up to two terminations, designated A and Z. At either termination, a circuit may connect to a site, device interface (via a cable), or to a provider network.
In adherence with NetBox's philosophy of closely modeling the real world, a circuit may be connected only to a physical interface. For example, circuits may not terminate to LAG interfaces, which are virtual in nature. In such cases, a separate physical circuit is associated with each LAG member interface and each needs to be modeled discretely.
A circuit in NetBox represents a physical link, and cannot have more than two endpoints. When modeling a multi-point topology, each leg of the topology must be defined as a discrete circuit, with one end terminating within the provider's infrastructure. The provider network model is ideal for representing these networks.
The circuit to which this termination belongs.
Designates the termination as forming either the A or Z end of the circuit.
If selected, the circuit termination will be considered "connected" even if no cable has been connected to it in NetBox.
The site with which this circuit termination is associated. Once created, a cable can be connected between the circuit termination and a device interface (or similar component).
Circuits which do not connect to a site modeled by NetBox can instead be terminated to a provider network representing an unknown network operated by a provider.
The operating speed of the terminated interface, in kilobits per second. This is useful for documenting the speed of a circuit when the actual interface to which it terminates is not being modeled in NetBox.
The upstream speed of the terminated interface (in kilobits per second), if different from the downstream speed (a common scenario with e.g. DOCSIS cable modems).
In a data center environment, circuits are often delivered via a local cross-connect. While it may not be appropriate to model the cross-connect itself in NetBox, it's a good idea to record its ID for reference where applicable.
Patch Panel & Port(s)
Similar to the cross-connect ID, this field can be used to track physical connection details which may be outside the scope of what is being modeled in NetBox.