Multicasttraffic is routed or bridged across private VLAN boundaries and within a single community VLAN.
Multicasttraffic is not forwarded between ports in the same isolated VLAN or between ports in different
secondaryVLANs.

Private VLANs and SVIs

Ina Layer3 switch, a switchvirtual interface (SVI) represents the Layer 3 interface of a VLAN. Layer3
devicescommunicate with a private VLAN only through the primary VLAN and not through secondary
VLANs.Configure Layer 3 VLAN interfaces (SVIs) only for primary VLANs. You cannot configure Layer 3
VLANinterfaces for secondary VLANs. SVIs for secondary VLANs are inactive while the VLAN is configured
asa secondaryVLAN.
•Ifyou tryto configurea VLAN with an active SVI as a secondary VLAN, the configuration is not
alloweduntil you disablethe SVI.
•Ifyou try to create an SVI on a VLAN that is configured as a secondary VLAN and the secondary VLAN
isalready mapped at Layer 3, the SVI is not created, and an error is returned. If the SVI is not mapped
atLayer 3, the SVI is created, but it is automatically shut down.
Whenthe primary VLAN isassociated with and mapped to the secondary VLAN, anyconfiguration on the
primaryVLAN is propagated to the secondary VLAN SVIs. For example, if you assign an IP subnet to the
primaryVLAN SVI, this subnet is theIP subnet address of theentire private VLAN.

Private VLANs and Switch Stacks

PrivateVLANs can operate within the switch stack, and private-VLAN ports can reside on different stack
members.However, some changes to the switch stack can impact private-VLAN operation:
•Ifa stackcontains only one private-VLANpromiscuous port and thestack member that contains that
portis removed from the stack, host ports inthat private VLAN lose connectivity outside the private
VLAN.
•Ifa stack master stack that contains the only private-VLAN promiscuous port in the stack fails or leaves
thestack and a new stack master is elected, host ports in a private VLAN that had its promiscuous port
onthe oldstack master lose connectivity outside of the private VLAN.
•Iftwo stacks merge, private VLANs on the winning stack are not affected, but private-VLAN
configurationon the losing switchis lost when thatswitch reboots.
Private VLAN Configuration Tasks
Toconfigure a private VLAN, perform these steps:
1SetVTP mode to transparent.
2Createthe primary and secondary VLANs and associate them.
Ifthe VLAN isnot created already, the private VLAN configuration process creates it.Note
Catalyst 2960-XR Switch VLAN Configuration Guide, Cisco IOS Release 15.0(2)EX1
92 OL-29440-01
Configuring Private VLANs
Private VLAN Configuration Tasks