Now that some core designs have been covered, the redundant designs for the distribution layer will be discussed. The distribution layer is covered more thoroughly in Chapter 4, "Applying the Principles of Network Design." Additional issues with redundancy and addressing are discussed in that chapter.
The two most common methods for providing redundancy at the distribution layer are dual homing and backup links to other distribution layer routers. The main consideration when designing redundancy in the distribution layer is unexpected traffic patterns.
Dual Homing to the Core
In Figure 3-8, Router A has two connections to the core through separate routers. While this provides very good redundancy—the loss of a single ...