Chapter 14 Configuring Private Vlans; Understanding Private Vlans - Cisco WS-C3020 Software Configuration Manual

Configuring Private VLANs
This chapter describes how to configure private VLANs on the Cisco Blade Switch.
For complete syntax and usage information for the commands used in this chapter, see the command
Note
reference for this release.
The chapter consists of these sections:
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When you configure private VLANs, the switch must be in VTP transparent mode. See
Note
"Configuring VTP."

Understanding Private VLANs

The private-VLAN feature addresses two problems that service providers face when using VLANs:
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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 and can have multiple VLAN
pairs—one for each subdomain. A subdomain is represented by a primary VLAN and a secondary
VLAN.
All VLAN pairs in a private VLAN share the same primary VLAN. The secondary VLAN ID
differentiates one subdomain from another. See
OL-8915-03
Understanding Private VLANs, page 14-1
Configuring Private VLANs, page 14-5
Monitoring Private VLANs, page 14-14
Scalability: 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
Figure 14-1.
Cisco Catalyst Blade Switch 3020 for HP Software Configuration Guide
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Chapter 12,
14-1