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 141 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
| 263 |
|
|