Dual Core

Dual Core
If you have more than two switch blocks and need redundant connections between the core and
distribution layer, you need to create a dual core. Figure 12.10 shows an example of a dual-core
configuration. Each connection would be a separate subnet.
In Figure 12.10, you can see that each switch block is redundantly connected to each of the
two core blocks. The distribution layer routers already have links to each subnet in the routing
tables, provided by the layer 3 routing protocols. If a failure on a core switch takes place, convergence
time will not be an issue. HSRP can be used to provide quick cutover between the
cores. (HSRP is covered in Chapter 20, “Quality of Service (QoS).”)