Understanding Private Vlans; Configuring Private Vlans - Cisco Catalyst 3560-X Software Configuration Manual

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This chapter describes how to configure private VLANs on the Catalyst 3750- or 3560-X switch. Unless

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

Catalyst 3750-X switch stack.

Private VLANs 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.

The chapter consists of these sections:

When you configure private VLANs on switches running VTP, the switch must be in VTP transparent

Understanding Private VLANs

The private-VLAN feature addresses two problems that service providers face when using VLANs:

Using private VLANs addresses the scalability problem and provides IP address management benefits

for service providers and Layer 2 security for customers. Private VLANs partition a regular VLAN

domain into subdomains. A subdomain is represented by a pair of VLANs: a primary VLAN and a

secondary VLAN. A private VLAN can have multiple VLAN pairs, one pair for each subdomain. All

VLAN pairs in a private VLAN share the same primary VLAN. The secondary VLAN ID differentiates

one subdomain from another. See

Understanding Private VLANs, page 1-1

Configuring Private VLANs, page 1-6

Monitoring Private VLANs, page 1-15

Chapter 1, "Configuring VTP."

Scalability: When running the IP base or IP services feature set, the switch supports up to 1005

active VLANs. If a service provider assigns one VLAN per customer, this limits the numbers of

customers the service provider can support.

To enable IP routing, each VLAN is assigned a subnet address space or a block of addresses, which

can result in wasting the unused IP addresses, and cause IP address management problems.

C H A P T E R

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

Catalyst 3750-x