15.14. Isolation in Advanced Zone Using Private VLAN
Isolation of guest traffic in shared networks can be achieved by using Private VLANs (PVLAN). PVLANs provide Layer 2 isolation between ports within the same VLAN. In a PVLAN-enabled shared network, a user VM cannot reach other user VM though they can reach the DHCP server and gateway, this would in turn allow users to control traffic within a network and help them deploy multiple applications without communication between application as well as prevent communication with other users’ VMs.
15.14.1. About Private VLAN
In an Ethernet switch, a VLAN is a broadcast domain where hosts can establish direct communication with each another at Layer 2. Private VLAN is designed as an extension of VLAN standard to add further segmentation of the logical broadcast domain. A regular VLAN is a single broadcast domain, whereas a private VLAN partitions a larger VLAN broadcast domain into smaller sub-domains. A sub-domain is represented by a pair of VLANs: a Primary VLAN and a Secondary VLAN. The original VLAN that is being divided into smaller groups is called Primary, which implies that all VLAN pairs in a private VLAN share the same Primary VLAN. All the secondary VLANs exist only inside the Primary. Each Secondary VLAN has a specific VLAN ID associated to it, which differentiates one sub-domain from another.
Three types of ports exist in a private VLAN domain, which essentially determine the behaviour of the participating hosts. Each ports will have its own unique set of rules, which regulate a connected host's ability to communicate with other connected host within the same private VLAN domain. Configure each host that is part of a PVLAN pair can be by using one of these three port designation:
Promiscuous: A promiscuous port can communicate with all the interfaces, including the community and isolated host ports that belong to the secondary VLANs. In Promiscuous mode, hosts are connected to promiscuous ports and are able to communicate directly with resources on both primary and secondary VLAN. Routers, DHCP servers, and other trusted devices are typically attached to promiscuous ports.
Isolated VLANs: The ports within an isolated VLAN cannot communicate with each other at the layer-2 level. The hosts that are connected to Isolated ports can directly communicate only with the Promiscuous resources. If your customer device needs to have access only to a gateway router, attach it to an isolated port.
Community VLANs: The ports within a community VLAN can communicate with each other and with the promiscuous ports, but they cannot communicate with the ports in other communities at the layer-2 level. In a Community mode, direct communication is permitted only with the hosts in the same community and those that are connected to the Primary PVLAN in promiscuous mode. If your customer has two devices that need to be isolated from other customers' devices, but to be able to communicate among themselves, deploy them in community ports.
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