An OSI system which is not an end system, but which serves instead to relay communications between end systems. See repeater, bridge, and router.

A node that is connected to more than one subnetwork with a primary role of forwarding data from one subnetwork to another. In Internet terminology, ISs are known as routers that relay data packets from ESs to their intended destinations.

A network device with the ability to forward packets between portions of a network. Bridges, switches, and routers are examples of intermediate systems.

An OSI system which performs network layer forwarding. It is analogous to an IP router. See also: Open Systems Interconnection, router.

In IS-IS, the network entity that sends and receives packets and can also route packets.

An OSI system that performs Internet layer forwarding. A routing system receives data packets from a system on one subnet and passes them on to a system on another subnet; it receives data packets from a source end system, or from the previous intermediate system on the route, and passes them on to the destination end system, or to the next intermediate system on the route.