VLAN Tagging

NOTE: A “VLAN tag” is also known as a “VLAN ID.” The terms are used interchangeably below.

Tagged and untagged virtual circuits

Tagged virtual circuit

A “tagged” virtual circuit is a virtual circuit with a VLAN ID greater than or equal to 1.

Because PacketFabric reserves tags 1-3, your virtual circuit VLAN IDs will be greater than or equal to 4 (our allowed VLAN ID range is 4-4094, inclusive).

Untagged virtual circuit

The term “untagged virtual circuit” is a bit misleading. The virtual circuit is, in fact, tagged - it’s just tagged with VLAN ID 0.

To create an untagged virtual circuit in the portal (or to create a virtual circuit with VLAN ID 0), you toggle the Make untagged option:

Animated gif of the untagged toggle

Uniqueness within tags

Understanding that an “untagged” virtual circuit is actually tagged with VLAN ID 0 is important because each VLAN ID must be unique on its port.

For example, you cannot tag two virtual circuits with VLAN ID 6 on a single port. Similarly, you cannot have two “untagged” virtual circuits on a port, because that would mean having two VLAN ID 0 circuits.

Tagged and untagged ports

Whether a port is “tagged” or “untagged” depends on the virtual circuits landing on that port.

Untagged ports

An untagged port is a port that has an untagged virtual circuit and no tagged virtual circuits.

Because each VLAN ID must be unique on its port, it is not possible to have a port with multiple untagged - or VLAN 0 - virtual circuits.

Therefore an untagged port is a port that only has a single, untagged virtual circuit:

Untagged port

Tagged ports

As soon as you land a virtual circuit with a tagged VLAN on a port, it becomes “tagged.”

In the case of PacketFabric ports, this is true regardless of whether that port also has an untagged virtual circuit:

tagged port

Tagging and building connections

In the PacketFabric network, virtual circuits follow these rules with regards to tagging:

  • Tagged-to-tagged port connections are always allowed.

  • Untagged-to-untagged port connections are never allowed.

  • Tagged-to-untagged port connections are usually allowed (see the note below).

    NOTE: EFR devices do not allow untagged/tagged VLAN combinations.

    You can check whether a port is on an EFR or CFR device from the port Details page. The device name should start with efr or cfr:

    Screenshot of the port device information

Because we allow tagged-to-untagged port connections, with a little planning, you can have fully untagged virtual circuits. You just need to ensure that one port has at least one tagged virtual circuit.

allowed vcs

Managing VLAN tags/IDs

You can edit the VLAN ID by editing the virtual circuit.

Edit VC