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Catalyst 3750-E and 3560-E Switch Software Configuration Guide
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Chapter16 Configuring Private VLANs
Configuring Private VLANs
Step5 If inter-VLAN routing will be used, configure the primary SVI, and map secondary VLANs to th e
primary. See the “Mapping Secondary VLANs to a Primary VLAN Layer 3 VLAN Interface” section on
page 16-14.
Step6 Verify private-VLAN configuration.
Default Private-VLAN Configuration
No private VLANs are configured.
Private-VLAN Configuration Guidelines
Guidelines for configuring private VLANs fall into these categories:
•Secondary and Primary VLAN Configuration, page 16-7
•Private-VLAN Port Configuration, page 16-8
•Limitations with Other Features, page 16-9

Secondary and Primary VLAN Configuration

Follow these guidelines when configuring private VLANs:
•Set VTP to transparent mode. After you configure a private VLAN, you should not change the VTP
mode to client or server. For information about VTP, see Chapter14, “Configuring VTP.”
•You must use VLAN configuration (config-vlan) mode to configure private VLANs. You cannot
configure private VLANs in VLAN database configuration mode. For more infor mation about
VLAN configuration, see “VLAN Configuration Mode Options” section on page 13-7.
•After you have configured private VLANs, use the copy running-config startup config privileged
EXEC command to save the VTP transparent mode configuration and private-VLAN configuration
in the switch startup configuration file. Otherwise, if the switch resets, it defaults to VTP server
mode, which does not support private VLANs.
•VTP does not propagate private-VLAN configuration. You must configure private VLANs on each
device where you want private-VLAN ports.
•You cannot configure VLAN 1 or VLANs 1002 to 1005 as primary or secondary VLANs. Extended
VLANs (VLAN IDs 1006 to 4094) can belong to private VLANs
•A primary VLAN can have one isolated VLAN and multiple community VLANs associated with it.
An isolated or community VLAN can have only one primary VLAN associated with it.
•Although a private VLAN contains more than one VLAN, only one Spanning Tree Protocol (STP)
instance runs for the entire private VLAN. When a secondary VL AN is associated with the primary
VLAN, the STP parameters of the primary VLAN are propagated to the secondary VLAN.
•You can enable DHCP snooping on private VLANs. When you enable DHCP snooping on the
primary VLAN, it is propagated to the secondary VLANs. If you configure DHCP on a secondary
VLAN, the configuration does not take effect if the primary VLAN is already configured.
•When you enable IP source guard on private-VLAN ports, you must enable DHCP snoopi ng on the
primary VLAN.