In network routing, the control plane is the part of the router architecture that is concerned with establishing the network topology, or the information in a routing table that defines what to do with incoming packets. Control plane functions, such as participating in routing protocols, run in the architectural control element. In most cases, the routing table contains a list of destination addresses and the outgoing interface or interfaces associated with each. Control plane logic can also identify certain packets to be discarded, as well as preferential treatment of certain packets for which a high quality of service is defined by such mechanisms as differentiated services.

Depending on the specific router implementation, there may be a separate forwarding information base that is populated by the control plane, but used by the high-speed forwarding plane to look up packets and decide how to handle them.

In computing, the control plane is the part of the software that configures and shuts down the data plane. By contrast, the data plane is the part of the software that processes the data requests. The data plane is also sometimes referred to as the forwarding plane.

The distinction has proven useful in the networking field where it originated, as it separates the concerns: the data plane is optimized for speed of processing, and for simplicity and regularity. The control plane is optimized for customizability, handling policies, handling exceptional situations, and in general facilitating and simplifying the data plane processing.

The conceptual separation of the data plane from the control plane has been done for years. An early example is Unix, where the basic file operations are open, close for the control plane and read, write for the data plane.

A major function of the control plane is deciding which routes go into the main routing table. "Main" refers to the table that holds the unicast routes that are active. Multicast routing may require an additional routing table for multicast routes. Several routing protocols e.g. IS-IS, OSPF and BGP maintain internal databases of candidate routes which are promoted when a route fails or when a routing policy is changed.

Several different information sources may provide information about a route to a given destination, but the router must select the "best" route to install into the routing table. In some cases, there may be multiple routes of equal "quality", and the router may install all of them and load-share across them.

There are three general sources of routing information: