Content

| Summary

This module discussed Layer 2 techniques and technologies designed to optimize network reliability, resiliency, and redundancy within a campus network.

In particular, this module explored:

- The importance of STP as a key Layer 2 network protocol
- Scaling issues with STP as they pertain to virtual LANs (VLANs); and VLAN Trunking Protocol (VTP).

STP enables Layer 2 reliability, resiliency, and redundancy in a campus network. STP dynamically configures a Layer 2 topology that blocks physical loops in a switched network while at the same time providing a number of configuration options for tailoring the flow of traffic in a network.

A Root Bridge serves as the focal point of the topology for each VLAN configured in PVST+ STP mode. With Path Cost, Port Priority, Bridge Priority, STP timers, PortFast, UplinkFast, and BackboneFast, the tools are available to design a robust Layer 2 topology.

EtherChannel provides the finishing touch to the Layer 2 switched infrastructure. EtherChannel provides for incremental bandwidth Ethernet link options, ranging from10 Mbps (half-duplex) 100-meter links to 160 Gbps (full-duplex) 50-kilometer links. EtherChannel relies on Port Aggregation Protocol (PAgP) to dynamically manage bundles of Ethernet links.

Several protocols are responsible for the wide variety of tools available in Layer 2 switched design and deployment. This module focused on STP and PAgP.