6.3 External Routers
6.3.4 When to use the router-on-a-stick design
In general, the router-on-a-stick approach to inter-VLAN routing is most appropriate when other options are not available. This is not to say that the router-on-a-stick design is a poor choice; it is only a reflection that other options tend to provide higher throughput and functionality. Also, because the router-on-a-stick technique functions as if the router were sitting on the edge of the network (at least as far as the Layer 2 network is concerned), it tends to be less tightly integrated with the rest of the campus network. Newer approaches, such as MLS, seek to place routing in the middle of the network where it can have a greater influence on the overall scalability and stability of the network.
Interactive Lab Activity  (Flash, 541 kB)
  In this activity, you will learn how to configure external inter-VLAN routing.