Information Technology Reference
In-Depth Information
the core layer allow for high availability in the event of a link failure. Infrastructure serv-
ices include quality of service (QoS) configuration, security, and policy enforcement. Ac-
cess lists are configured in the distribution layer.
Core
Layer
Building
Distribution
Building
Access
Workstations
Figure 3-6
Distribution Layer
The following are recommended best practices at the distribution layer:
Use first-hop redundancy protocols. Hot Standby Router Protocol (HSRP) or Gate-
way 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.
■
Build Layer 3 triangles, not squares, as shown in bold in Figure 3-7.
■
Core
Distribution
Triangle Links
Square Connectivity
(Do Not Use)
Figure 3-7
Layer 3 Triangles
