• Conservation of Layer 2 overlay tunnels and peer networks with a single virtual network identifier (VNI) mapped to Primary VLAN. Primary and Secondary VLANs Each subdomain in a PVLAN is represented by a pair of VLANs: a primary VLAN and a secondary VLAN. A PVLAN can have multiple VLAN pairs, one pair for each subdomain. All VLAN pairs in a PVLAN share the same primary VLAN. The secondary VLAN ID differentiates one subdomain from another. A secondary VLAN can either be an isolated VLAN or a community VLAN. Primary and secondary VLANs have the following characteristics: • Primary VLAN: A PVLAN has only one primary VLAN. Every port in a PVLAN is a member of the primary VLAN.
The primary VLAN carries unidirectional traffic downstream from the promiscuous ports to the host (isolated and community) ports and to other promiscuous ports. • Isolated VLAN: A PVLAN has only one isolated VLAN. An isolated VLAN is a secondary VLAN that carries unidirectional traffic upstream from the hosts towards the promiscuous ports and the gateway. • Community VLAN: A community VLAN is a secondary VLAN that carries upstream traffic from the community ports to the promiscuous port gateways and to other host ports in the same community. You can configure multiple community VLANs in a PVLAN. Private VLAN Ports PVLAN ports are access ports that are one of these types: • Promiscuous:
A promiscuous port belongs to the primary VLAN. It can communicate with all interfaces, including the community and isolated host ports that belong to the secondary VLANs associated with the primary VLAN. • Isolated: An isolated port is a host port that belongs to an isolated secondary VLAN. It has complete Layer 2 separation from other ports within the same PVLAN, except for the promiscuous ports. PVLANs block all traffic to isolated ports except traffic from promiscuous ports. Likewise, PVLANs forward the traffic from an isolated port only to promiscuous ports. • Community: A community port is a host port that belongs to a community secondary VLAN.
Community ports communicate with other ports in the same community VLAN and with promiscuous ports. Community ports are isolated at Layer 2 from all other interfaces in external communities and also from isolated ports within their private VLAN. For more information about PVLANs and the steps to configure PVLANs, see "Configuring Private VLANs" module in the VLAN Configuration Guide for the applicable release. Extension of Private VLANs in a BGP EVPN VXLAN Fabric Private VLANs (PVLANs) partition a regular VLAN domain into subdomains and provide Layer 2 isolation between ports within the same PVLAN. Like a regular VLAN, a private VLAN can span multiple Layer 2 switches.
In a private VLAN that spans across multiple devices, traffic from an isolated port in Switch A does not reach an isolated port on Switch B. This is achieved by the trunk port carrying the primary VLAN and secondary VLANs to neighboring switches with dot1q tag in a traditional Layer 2 network. With BGP EVPN VXLAN enabled in the PVLANs on the VTEPs, the L2VNI segment preserves the PVLAN semantics and Configuring Private VLANs in a BGP EVPN VXLAN Fabric Primary and Secondary VLANs Configuring Private VLANs in a BGP EVPN VXLAN Fabric 2