16-9
Catalyst 3750 SwitchSoftware Configuration Guide
OL-8550-09
Chapter16 Configuring Private VLANs
Configuring Private VLANs
Private-VLAN Port Configuration
Follow these guidelines when configuring private-VLAN ports:
Use only the private-VLAN configuration commands to assign ports to primary, isolated, or
community VLANs. Layer 2 access ports assigned to the VLANs that you configure as primary,
isolated, or community VLANs are inactive while the VLAN is part of the private-VLAN
configuration. Layer 2 trunk interfaces remain in the STP forwarding state.
Do not configure ports that belong to a PAgP or LACP EtherChannel as private-VLAN ports. While
a port is part of the private-VLAN configuration, any EtherChannel configuration for it is inactive.
Enable Port Fast and BPDU guard on isolated and community host ports to prevent STP loops due
to misconfigurations and to speed up STP convergence (see Chapter20, “Configuring Optional
Spanning-Tree Features”). When enabled, STP applies the BPDU guard feature to all Port
Fast-configured Layer 2 LAN ports. Do not enable Port Fast and BPDU guard on promiscuous ports.
If you delete a VLAN used in the private-VLAN configuration, the private-VLAN ports associated
with the VLAN become inactive.
Private-VLAN ports can be on different network devices if the devices are trunk-connected and the
primary and secondary VLANs have not been removed from the trunk.
Limitations with Other Features
When configuring private VLANs, remember these limitations with other features:
Note In some cases, the configuration is accepted with no error messages, but the commands have no effect.
Do not configure fallback bridging on switches with private VLANs.
When IGMP snooping is enabled on the switch (the default), the switch stack supports no more than
20 private-VLAN domains.
Do not configure a remote SPAN (RSPAN) VLAN as a private-VLAN primary or secondary VLAN.
For more information about SPAN, see Chapter29, “Configuring SPAN and RSPAN.”
Do not configure private-VLAN ports on interfaces configured for these other features:
dynamic-access port VLAN membership
Dynamic Trunking Protocol (DTP)
Port Aggregation Protocol (PAgP)
Link Aggregation Control Protocol (LACP)
Multicast VLAN Registration (MVR)
voice VLAN
Web Cache Communication Protocol (WCCP)
A private-VLAN port cannot be a secure port and should not be configured as a protected port.
You can configure IEEE 802.1x port-based authentication on a private-VLAN port, but do not
configure IEEE 802.1x with port security, voice VLAN, or per-user ACL on private-VLAN ports.