The switches functions are segregated into different planes (groups). The Control pane is the most common plane.
- Control Plane: includes internal monitoring and control functions related to power, temperature, and hardware.
- Forwarding plane: The group of functions includes L2 and L3 forwarding, packet generally filtering, and QoS policies. This plane usees the routing table and functions in hardware due to speed requirements.
- Management plane: provides platform to manage all L2 and L3 protocols (STP, OSPF, etc.). The routing table is built in this plane. This plane’s functions are software based to allow for upgrades.
In stackable switches, the CPU runs the management and control planes, and ASICs are in charge of packet processing and forwarding.
A modular switch combines the management and control planes into Switching and Routing Processing Units (SRPUs). The forwarding plane is distributed in two or more Line Processing Units (LPUs). Modular switches generally support at least two SRPUs for redundancy.
