6.3 External Routers
6.3.2 Router on a stick
As you may have guessed, early VLAN designs relied on external routers connected to VLAN-capable switches in the manner shown in the Figure. In this approach, traditional routers are connected via one or more links to a switched network. The Figure shows a single link, the stick, connecting the router to the rest of the campus network. Inter-VLAN traffic must cross the Layer 2 backbone to reach the router where it can move between VLANs. It then travels back to the desired end station using normal Layer 2 forwarding. This "out-to-the-router-and-back" flow is characteristic of all router-on-a-stick designs.

The Figure illustrates the router connection in a general sense. This section examines using the Fast Ethernet interface of the router as a trunk link.