Reference Guide

Private VLANs | 629
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Private VLANs
FTOS 7.8.1.0 adds a Private VLAN (PVLAN) feature for the C-Series and S-Series: c s z
For syntax details on the commands discussed in this chapter, see the Private VLANs Commands chapter
in the FTOS Command Reference.
This chapter contains the following major sections:
• Private VLAN Concepts on page 630
• Private VLAN Commands on page 631
• Private VLAN Configuration Task List on page 632
• Private VLAN Configuration Example on page 635
• Inspecting the Private VLAN Configuration on page 636
Private VLANs extend the FTOS security suite by providing Layer 2 isolation between ports within the
same VLAN. A private VLAN 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 is forwarded only to promiscuous ports or trunk ports.
Example uses of PVLANs:
• A hotel can use an isolated VLAN in a private VLAN to provide Internet access for its guests, while
stopping direct access between the guest ports.
• A service provider can provide Layer 2 security for customers and use the IP addresses more
efficiently, by using a separate community VLAN per customer, while at the same time using the same
IP subnet address space for all community and isolated VLANs mapped to the same primary VLAN.
In more detail, community VLANs are especially useful in the service provider environment, because,
multiple customers are likely to maintain servers that must be strictly separated in customer-specific
groups. A set of servers owned by a customer could comprise a community VLAN, so that those serv-
ers could communicate with each other, and would be isolated from other customers. Another cus-
tomer might have another set of servers in another community VLAN. Another customer might want
an isolated VLAN, which is has one or more ports that are also isolated from each other.