ZyXEL Communications GS1920-48HPv2, Руководство пользователя

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Chapter 28 Layer 2 Protocol Tunneling
GS1920v2 Series User’s Guide
262
C
HA PTER
2 8
La ye r 2 Pro to c o l Tunne ling
28.1 La ye r 2 Pro to c o l Tunne ling O ve rvie w
This chapter shows you how to configure layer 2 protocol tunneling on the Switch.
28.1.1 Wha t Yo u C a n Do
Use the
La ye r 2 Pro to c o l Tunne l
screen ( Section 28.2 on page 263 ) 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.
28.1.2 Wha t Yo u Ne e d to Kno w
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.
Fig ure 189
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.