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
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
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:
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
Tagged and untagged ports
Whether a port is “tagged” or “untagged” depends on the virtual circuits landing on that port.
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:
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:
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
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.
Managing VLAN tags/IDs
You can edit the VLAN ID by editing the virtual circuit.