The following table describes VC modes that are supported on PWs.
| VC mode | Description |
|---|---|
| Raw | At VC label imposition, when a tagged packet is received on a tagged AC endpoint, the VLAN tag is removed before it is sent out on the wire. When an untagged packet is received on an untagged AC endpoint it is encapsulated as is and sent out on the wire. |
| Raw-passthrough | Enables interoperation with third-party devices. When a packet that is destined for a remote peer is received on either a tagged or untagged AC endpoint, it is encapsulated in an MPLS header and sent on to the MPLS cloud without adding or removing VLAN tags. When a packet that is destined for a local endpoint is received on either a tagged or untagged AC endpoint, the MPLS header is removed before sending it on to the local endpoint; VLAN tags in the original packet are not changed in any way. |
| Tagged | At VC label imposition, when a tagged packet is received on a tagged AC endpoint, the packet is encapsulated as is and sent out on the wire. When a packet is from a dual-tagged AC endpoint, the outer VLAN tag is removed and only the inner VLAN TAG is sent out on the wire. When an untagged packet is received on an untagged AC endpoint, a dummy tag is added and it is sent out on the wire. |
The VC mode is agreed by PE peer devices during the pseudowire signaling process.
A single VPLS instance can have a mixture of tagged and untagged endpoints.
When the VC mode is changed on a device, the PWs are torn down are re-established except in the cases of a change from raw to raw-passthrough or a change from raw-passthrough to raw. The traffic impact is minimal (because PWs are not torn down and re-established) when the VC mode is changed from raw to raw-passthrough (or vice versa).
VC mode is configured by specifying the vc-mode option for the pw-profile command.
Note
When a pseudowire profile is attached to a bridge domain, on which routing is enabled (by using the router-interface command), you are not allowed to change the pseudowire profile vc-mode configuration to raw.