A computer network is a collection of interconnected computing devices that can exchange data and share resources. Example network devices include layer two devices that operate within the second layer of the Open Systems Interconnection (OSI) reference model, i.e., the data link layer, and layer three devices that operate within the third layer of the OSI reference model, i.e., the network layer. Network devices within computer networks often include a control unit that provides control plane functionality for the network device and forwarding units for routing or switching data units. In some cases, for example, a network device may include a plurality of forwarding units and a switch fabric that collectively provide a forwarding plane for forwarding network packets.
For example, the control plane functions provided by the control unit of a router include storing network topologies in the form of a routing information base (RIB), executing routing protocols to communicate with peer routing devices to maintain and update the RIB, providing a management interface to allow user access and configuration of the network device, responding to Address Resolution Protocol (ARP) requests, and/or other control plane functions. Thus, in addition to receiving and processing network packets destined for other network devices, including end-user devices, application servers, database servers, routers, and so forth, a network device also receives network packets directed to the network device itself. The control plane receives these “host-bound” packets (collectively, host-bound traffic) from the forwarding plane and processes the host-bound traffic to carry out control plane functions.