Distribution Layer for the Campus Network

Distribution Layer for the Campus Network
Within a campus network, the Distribution layer is the workhorse that will take all Access layer
layer 2 switches and aggregate their bandwidth to the Core layer. The Distribution layer is
either a large router or a layer 3 switch. Because this is the first layer 3 device the traffic has
encountered, layer 3 access controls are applied at this layer.
When using a layer 3 switch, VLANs can be utilized to allow hosts on multiple Access layer
switches to use the same layer 3 network address space. This can enhance security by allowing
only the hosts on the VLAN to communicate directly with one another. Communications
between subnets can then be subject to layer 3 access control.
You can optionally configure the marking of packets for quality of service (QoS) at this layer,
but it is not advised because the Access layer is a better place for this service. Instead, you can
configure queuing to ensure that higher priority traffic will be processed first if there is congestion
on the links.
Redundancy is achieved by using a layer 2 redundancy technology such as STP on both the
Core and the Access layers. Multiple interfaces can be aggregated through inverse multiplexing
if greater bandwidth is needed to the core of the network.