6.1 VLAN Issues
6.1.1 Importance of routing
Probably the most important benefit of routing is its proven history of facilitating networks, particularly large networks. Although the Internet serves as the obvious example here, this point is true for any type of network, such as a large campus backbone. Because routers prevent broadcast propagation and use more intelligent forwarding algorithms than bridges and switches, routers provide much more efficient use of bandwidth. This simultaneously results in flexible and optimal path selection. For example, it is very easy to implement load balancing across multiple paths in most networks when using routing. On the other hand, Layer 2 load balancing can be very difficult to design, implement, and maintain. The data-forwarding benefits of routers are especially important when multicast traffic is in use. As multicast traffic becomes increasingly common in campus networks, routers will continue to play an important role.

Routers provide additional benefits that reach beyond the area of data forwarding. If Layer 3 addresses are hierarchical, routers can be used to implement designs that utilize route summarization. Reducing routing protocol overhead, increasing table lookup performance, and improving network stability can further facilitate networks of almost unlimited size. Most routers provide extensive access-list capabilities that can be used to provide important policy controls. Finally, routers can also provide important features such as Dynamic Host Configuration Protocol (DHCP) relay, proxy Address Resolution Protocol (ARP), and Get Nearest Server (GNS) functions in Internetwork Packet Exchange (IPX) networks.