36Private VLANs (PVLAN)The private VLAN (PVLAN) feature is supported on Dell Networking OS.For syntax details about the commands described in this chapter, refer to the Private VLANs commands chapter in the DellNetworking OS Command Line Reference Guide.Private VLANs extend the Dell Networking OS security suite by providing Layer 2 isolation between ports within the same virtuallocal area network (VLAN). A PVLAN partitions a traditional VLAN into subdomains identified by a primary and secondary VLAN pair.Private VLANs block all traffic to isolated ports except traffic from promiscuous ports. Traffic received from an isolated port isforwarded only to promiscuous ports or trunk ports.Example uses of PVLANs:• A hotel can use an isolated VLAN in a PVLAN to provide Internet access for its guests, while stopping direct access between theguest ports.• A service provider can provide Layer 2 security for customers and use the IP addresses more efficiently, by using a separatecommunity VLAN per customer and at the same time using the same IP subnet address space for all community and isolatedVLANs mapped to the same primary VLAN.– In more detail, community VLANs are especially useful in the service provider environment because multiple customers arelikely to maintain servers that must be strictly separated in customer-specific groups. A set of servers owned by a customercould comprise a community VLAN, so that those servers could communicate with each other, and would be isolated fromother customers. Another customer might have another set of servers in another community VLAN. Another customer mightwant an isolated VLAN, which has one or more ports that are also isolated from each other.Private VLAN ConceptsReview the following PVLAN concepts before you create PVLANs on your system.The VLAN types in a PVLAN include:• Community VLAN — a type of secondary VLAN in a primary VLAN:– Ports in a community VLAN can communicate with each other.– Ports in a community VLAN can communicate with all promiscuous ports in the primary VLAN.– A community VLAN can only contain ports configured as host.• Isolated VLAN — a type of secondary VLAN in a primary VLAN:– Ports in an isolated VLAN cannot talk directly to each other.– Ports in an isolated VLAN can only communicate with promiscuous ports in the primary VLAN.– An isolated VLAN can only contain ports configured as host.• Primary VLAN — the base VLAN of a PVLAN:– A switch can have one or more primary VLANs, and it can have none.– A primary VLAN has one or more secondary VLANs.– A primary VLAN and each of its secondary VLANs decrement the available number of VLAN IDs in the switch.– A primary VLAN has one or more promiscuous ports.– A primary VLAN might have one or more trunk ports, or none.• Secondary VLAN — a subdomain of the primary VLAN.Private VLANs (PVLAN) 559
