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CHAPTER

19-1

Catalyst 3750-X and 3560-X Switch Software Configuration Guide

OL-21521-01

Configuring IEEE 802.1Q and Layer 2 Protocol

Tunneling

Virtual private networks (VPNs) provide enterprise-scale connectivity on a shared infrastructure, often

Ethernet-based, with the same security, prioritization, reliability, and manageability requirements of

private networks. Tunneling is a feature designed for service providers who carry traffic of multiple

customers across their networks and are required to maintain the VLAN and Layer 2 protocol

configurations of each customer without impacting the traffic of other customers. The Catalyst 3750-X

or 3560-X switch suppor

ts IEEE 802.1Q tunneling and Layer 2 protocol tunneling. Unless otherwise

noted, the term switch refers to a Catalyst 3750-X or 3560-X standalone switch and to a Catalyst 3750-X

itch stack.

Note IEEE 802.1Q and Layer 2 protocol tunneling are not supported on switches running the LAN base

feature set.

For complete syntax and usage information for the commands used in this chapter, see the command

reference for this release.

This chapter contains these sections:

• Understanding IEEE 802.1Q Tunneling, page 19-1

• Configuring IEEE 802.1Q Tunneling, page 19-4

• Understanding Layer 2 Protocol Tunneling, page 19-8

• Configuring Layer 2 Protocol Tunneling, page 19-10

• Monitoring and Maintaining Tunneling Status, page 19-18

Understanding IEEE 802.1Q Tunneling

Business customers of service providers often have specific requirements for VLAN IDs and the number

of VLANs to be supported. The VLAN ranges required by different customers in the same

service-provider network might overlap, and traffic of customers through the infrastructure might be

mixed. Assigning a unique range of VLAN IDs to each customer would restrict customer configurations

and could easily exceed the VLAN limit (4096) of the IEEE 802.1Q specification.

Using the IEEE 802.1Q tunneling feature, service providers can use a single VLAN to support customers

ho have multiple VLANs. Customer VLAN IDs are preserved, and traffic from different customers is

segregated within the service-provider network, even when they appear to be in the same VLAN. Using

IEEE 802.1Q tunneling expands VLAN space by using a VLAN-in-VLAN hierarchy and retagging the

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