CCNP/CCIE ENCOR Exam Series: Hierarchical LAN Design
This article discusses topics covered in Chapter 22 of the CCNP & CCIE ENCOR OCG.
Exam Topic 1.1: Enterprise network design such as Tier 2, Tier 3 & Fabric Capacity Planning
Key Points about Hierarchical LAN Design
The Hierarchical Model divides your network into 3 modular layers Access, Distribution, and Core. Each layer serves a specific function and these layers can be easily replicated throughout your network.
Access Layer: Gives endpoints and users access to the network via wired and wireless technologies
Distribution Layer: Provides an aggregation point for the access layer as well as a boundary between the access and core layer.
Core Layer: Provides connectivity to the distribution layers in large environments and home to the core network services (Data Center, Internet etc)
What are the Benefits?
This model offers the following benefits:
Simplified Management and Troubleshooting
Provides fault containment
Minimized effect of changes
Gives endpoints and users access to the network via wired and wireless technologies
Commonly referred to as the Network Edge
Provides high bandwidth connectivity using wired and wireless technologies
QoS is typically in place here to enhance the QoE
Segmented with VLANs
Plays a major role in the security of the network
Aggregation Point for the access layer provides a service and control boundary between the core and access layers
Aggregates the Access layer switches
Provides a boundary between the L2 Domain and the L3 domain of the core
Prevents the propagation of L2 faults -> STP, Loops
Provides a point of route summarization for IP info as it enters the core
Reduction in protocol overhead
Switches at the layer should be deployed in pairs for redundancy and fully connected to the access switches with L2 or L3 Links
The backbone and aggregation for multiple networks
Provides scalability, HA, and Fast Convergence
Provides interconnectivity between the access layer and the data center, public & private clouds, WAN and other network services
Reduces network complexity
Should be considered once a network grows to 3 distribution layers.
There are 6 different approaches to the Design Model:
Two-Tier (Collapsed Core)
Layer 2, STP Based
Layer 3, Routed Access
Simplified Campus Design
We'll dive more into these Design Options in my next article.