Chapter 5. Path Control

In general, link redundancy is a good thing, but it can also lead to some network problems. You might want to manually control the route taken by some or all of your traffic to provide a predictable and deterministic traffic flow. Path control can prevent suboptimal routing, ensure path availability, provide optimized performance for specific applications, and provide load sharing among various paths.

A good path control strategy understands that traffic is bidirectional and considers both inbound and outbound traffic. Asymmetric routing—where traffic exits via one link and enters via another—is not inherently bad. But you might need to minimize it when using stateful devices such as firewalls, or with sensitive applications such as voice. A good routing plan requires a good design. Design IP addresses that can be summarized and use redistribution and passive interfaces appropriately.