| 6.3 | External Routers | ||
| 6.3.2 | Router on a stick |
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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.
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