XS1930 Series User’s Guide
214
C
HAPTER
27
Layer 2 Protocol Tunneling
27.1 Layer 2 Protocol Tunneling 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 (
) 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 152
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.
