Scaling Layer 3 Backbones

Scaling Layer 3 Backbones
As discussed in the previous section, “Scaling Layer 2 Backbones,” you’ll typically find layer 2
switches connecting to layer 3 switches, which connect to the core with the layer 2 switches.
However, it is possible that some networks might have layer 2/layer 3/layer 3 designs (layer 2
connecting to layer 3 connecting to layer 3). But this is not cheap, even if you’re using someone
else’s money. There is always some type of network budget, and you need to have good reason
to spend the type of money needed to build layer 3 switches into the core.
There are three reasons you would implement layer 3 switches into the core:
 Fast convergence
 Automatic load balancing
 Elimination of peering problems