ZyXEL XGS4700-48F User Guide - Page 293
Layer 2 Protocol Tunneling
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CHAPTER 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 XGS4700-48F User's Guide 293