Advanced IP Network Design (CCIE Professional Development)

Access Redundancy

The access layer presents many of the same challenges and issues as the distribution layer, and it also shares some of the same strategies for resolving these drawbacks. Dual homing access layer devices are the most common way of providing redundancy to remote locations, but it's also possible to interconnect access layer devices to provide redundancy.

In Figure 3-10, Router G and Router H are access layer routers that are dual-homed with the backup circuit connected to different branches of the distribution layer. If these redundant links are actually constantly up and carrying traffic, the number of paths between 10.2.1.0/24 and 10.1.1.0/24 is excessive:

• Router H to Router F to Router B to Router A to Router C to Router G ...