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GS2200-8/24 User’s Guide 219

CHAPTER 27

Layer 2 Protocol Tunneling

27.1 Overview

This chapter shows you how to configure layer 2 protocol tunneling on the Switch.

27.1.1 What You Can Do

Use the Layer 2 Protocol Tunnel screen (Section 27.2 on page 221) to enable layer 2 protocol

tunneling on the Switch and specify a MAC address with which the Switch uses to encapsulate the

layer 2 protocol packets by replacing the destination MAC address in the packets.

27.1.2 What You Need to Know

Layer 2 protocol tunneling (L2PT) is used on the service provider's edge devices.

L2PT allows edge switches (1 and 2 in the following figure) to tunnel layer 2 STP (Spanning Tree

Protocol), CDP (Cisco Discovery Protocol) and VTP (VLAN Trunking Protocol) packets between

customer switches (A, B and C in the following figure) connected through the service provider’s

network. The edge switch encapsulates layer 2 protocol packets with a specific MAC address before

sending them across the service provider’s network to other edge switches.

Figure 139 Layer 2 Protocol Tunneling Network Scenario

In the following example, if you enable L2PT for STP, you can have switches A, B, C and D in the

same spanning tree, even though switch A is not directly connected to switches B, C and D.

Topology change information can be propagated throughout the service provider’s network.

Service Provider's

Network

STP

CDP

VTP

STP

VTP

CDP