About Virtual Local Area Networks (VLANs)

An 802.1Q VLAN (virtual local area network) is a collection of computers on a LAN or LANs that are grouped together in a single broadcast domain independent of their physical location. This enables you to group devices according to traffic patterns, instead of physical proximity. Members of a VLAN can share resources as if they were connected to the same LAN. You can also use VLANs to split a switch into multiple segments. For example, suppose your company has full-time employees and contract workers on the same LAN. You want to restrict the contract employees to a subset of the resources used by the full-time employees. You also want to use a more restrictive security policy for the contract workers. In this case, you split the interface into two VLANs.

VLANs enable you to divide your network into groups with a logical, hierarchical structure or grouping instead of a physical one. This helps free IT staff from the restrictions of their existing network design and cable infrastructure. VLANs make it easier to design, implement, and manage your network. Because VLANs are software-based, you can quickly and easily adapt your network to additions, relocations, and reorganizations.

VLANs use bridges and switches, so broadcasts are more efficient because they go only to people in the VLAN, not everyone on the wire. Consequently, traffic across your routers is reduced, which means a reduction in router latency. You can configure your XTM device to act as a DHCP server for devices on the VLAN, or use DHCP relay with a separate DHCP server.

You assign a VLAN to the Trusted, Optional, or External security zone. VLAN security zones correspond to aliases for interface security zones. For example, VLANs of type Trusted are handled by policies that use the alias Any-Trusted as a source or destination. VLANs of type External appear in the list of external interfaces when you configure policy-based routing.

VLAN Requirements and Restrictions 

If you define VLANs, you can ignore messages with the text 802.1d unknown version. These occur because the WatchGuard VLAN implementation does not support spanning tree link management protocol.

About Tagging 

To enable VLANs, you must deploy VLAN-capable switches in each site. The switch interfaces insert tags at layer 2 of the data frame that identify a network packet as part of a specified VLAN. These tags, which add an extra four bytes to the Ethernet header, identify the frame as belonging to a specific VLAN. Tagging is specified by the IEEE 802.1Q standard.

The VLAN definition includes disposition of tagged and untagged data frames. You must specify whether the VLAN receives tagged, untagged, or no data from each interface that is enabled. Your XTM device can insert tags for packets that are sent to a VLAN-capable switch. Your device can also remove tags from packets that are sent to a network segment that belongs to a VLAN that has no switch.

An XTM device interface can handle traffic for multiple tagged VLANs. This allows the interface to function as a VLAN trunk. The XTM device supports the 802.1Q standard.

About VLAN ID Numbers

By default, on most new switches that are not configured, each interface belongs to VLAN number 1. Because this VLAN exists on every interface of most switches by default, the possibility exists that this VLAN can accidentally span the entire network, or at least very large portions of it.

We recommend you use a VLAN ID number that is not 1 for any VLAN that passes traffic to the XTM device.

See Also

Define a New VLAN

Common Interface Settings

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