29

Layer 2 Protocol Tunneling

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

29.1 Layer 2 Protocol Tunneling Overview

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 142 Layer-2 Protocol Tunneling Network Scenario

A

 

Service Provider's

C

STP

 

 

Network

 

CDP

1

 

STP

2

 

 

 

 

CDP

VTP

VTP

 

B

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.

To emulate a point-to-point topology between two customer switches at different sites, such as A and B, you can enable protocol tunneling on edge switches 1 and

 

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XGS4700-48F User’s Guide