Explanation/Reference:
Explanation:
Distribution Layer Best Practices
As shown in Figure 3-6, the distribution layer aggregates all closet switches and connects to the core layer.
Design considerations for the distribution layer include providing wirespeed performance on all ports, link redundancy, and infrastructure services. The distribution layer should not be limited on performance. Links to the core must be able to support the bandwidth used by the aggregate access layer switches.
Redundant links from the access switches to the distribution layer and from the distribution layer to the core layer allow for high availability in the event of a link failure. Infrastructure services include quality of service (QoS) configuration, security, and policy enforcement. Access lists are configured in the distribution layer.

The following are recommended best practices at the distribution layer:
Use first-hop redundancy protocols. Hot Standby Router Protocol (HSRP) or Gateway Load Balancing Protocol (GLBP) should be used if you implement Layer 2 links between the Layer 2 access switches and the distribution layer.
Use Layer 3 routing protocols between the distribution and core switches to allow for fast convergence and load balancing.
Only peer on links that you intend to use as transit.