What is the router-on-a-stick design?

• A. Routing between multiple VLANs on a single router via subinterfaces with 802.1Q tagging.
• B. Connecting multiple routers in a hub-and-spoke topology
• C. A switch with a single VLAN routing
• D. A router that only supports one subnet

Answer: (B)

Router-on-a-stick is a method for inter-VLAN routing using a single router connection to a switch. Instead of giving the router a separate physical interface for each VLAN, you create multiple logical subinterfaces on one router interface, and each subinterface is assigned to a different VLAN using 802.1Q tagging. The switch port that links to the router is a trunk, carrying all the VLANs. Each subinterface gets its own IP address, which acts as the default gateway for devices in that VLAN. This setup lets the router route traffic between VLANs over one physical link, saving hardware and simplifying the design when you have several VLANs.