Distribution Layer

Distribution Layer
The distribution layer is sometimes referred to as the workgroup layer and is the communication
point between the access layer and the core. The primary function of the distribution layer
is to provide routing, filtering, and WAN access and to determine how packets can access the
core, if needed. The distribution layer must determine the fastest way that user requests are serviced
(for example, how a file request is forwarded to a server). After the distribution layer
determines the best path, it forwards the request to the core layer. The core layer is then responsible
for quickly transporting the request to the correct service.
The distribution layer is the place to implement policies for the network. Here, you can exercise
considerable flexibility in defining network operation. Generally, the following should be
done at the distribution layer:
 Implement tools such as access lists, packet filtering, and queuing.
 Implement security and network policies, including address translation and firewalls.
 Redistribute between routing protocols, including static routing.
 Route between VLANs and other workgroup support functions.
 Define broadcast and multicast domains.
Things to avoid at the distribution layer are limited to those functions that exclusively belong
to one of the other layers.