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Technical Documentation > SonicOS 7 System > Interfaces > About Interfaces > Physical and Virtual Interfaces > Virtual Interfaces (VLAN)

Virtual Interfaces (VLAN)

Supported on SonicWall Security Appliances, virtual Interfaces are subinterfaces assigned to a physical interface. Virtual interfaces allow you to have more than one interface on one physical connection.

Virtual interfaces provide many of the same features as physical interfaces, including zone assignment, DHCP Server, and NAT and Access Rule controls.

Virtual Local Area Networks (VLANs) can be described as a “tag-based LAN multiplexing technology” because through the use of IP header tagging, VLANs can simulate multiple LAN’s within a single physical LAN. Just as two physically distinct, disconnected LAN’s are wholly separate from one another, so too are two different VLANs; however, the two VLANs can exist on the very same wire. VLANs require VLAN aware networking devices to offer this kind of virtualization — switches, routers and firewalls that have the ability to recognize, process, remove and insert VLAN tags (IDs) in accordance with the network’s design and security policies.

VLANs are useful for a number of different reasons, most of which are predicated on the VLANs ability to provide logical rather than physical broadcast domain, or LAN boundaries. This works both to segment larger physical LAN’s into smaller virtual LAN’s, as well as to bring physically disparate LAN’s together into a logically contiguous virtual LAN. The benefits of this include:

  • Increased performance – Creating smaller, logically partitioned broadcast domains decreases overall network utilization, sending broadcasts only where they need to be sent, thus leaving more available bandwidth for application traffic.
  • Decreased costs – Historically, broadcast segmentation was performed with routers, requiring additional hardware and configuration. With VLANs, the functional role of the router is reversed – rather than being used for the purposes of inhibiting communications, it is used to facilitate communications between separate VLANs as needed.
  • Virtual workgroups – Workgroups are logical units that commonly share information, such as a Marketing department or an Engineering department. For reasons of efficiency, broadcast domain boundaries should be created such that they align with these functional workgroups, but that is not always possible: Engineering and Marketing users might be commingled, sharing the same floor (and the same workgroup switch) in a building, or just the opposite – the Engineering team might be spread across an entire campus. Attempting to solve this with complex feats of wiring can be expensive and impossible to maintain with constant adds and moves. VLANs allow for switches to be quickly reconfigured so that logical network alignment can remain consistent with workgroup requirements.
  • Security – Hosts on one VLAN cannot communicate with hosts on another VLAN unless some networking device facilitates communication between them.

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