Dell PowerConnect 5548 User Guide - Page 462

QinQ Tagging QinQ tagging enables you to add an additional tag to previously-tagged packets. The added tag provides a VLAN ID to each customer, which ensures private and segregated network traffic. The VLAN ID tag is assigned to a customer port in the service provider network. The designated port then provides additional services to the packets with the double-tags. This enables administrators to expand service to VLAN users. Port Modes Ports participating in Layer 2 switching may be classified as: • Access Ports Ports set to Access mode belong to a single VLAN, whose VID is the currently set PVID (default =1). These ports accept all untagged frames, and all frames tagged with the VID, currently set as the port's PVID. All traffic is sent untagged. If the VLAN, whose VID is set as the current PVID of the port, is deleted from the system, or deleted from the port, the port's PVID will be set to 1, meaning that the port will be made a member of VLAN#1, the default VLAN. Ingress filtering is always enabled for ports in Access mode. Setting an Access port's PVID to 4095 effectively shuts it down, as no frames will be transferred in either direction. Access mode ports are intended to connect end-stations to the system, especially when the end-stations are incapable of generating VLAN tags. • Trunk Ports Ports set to Trunk mode may belong to multiple VLANs. The default VLAN membership of a trunk port is all VLANs (1-4094). A PVID must be set on the port (it can be a non-existing VLAN). Trunk ports accept tagged and untagged frames. Untagged frames will be classified to the VLAN whose VLAN ID (VID) is configured as the port's PVID. Frames, sent from the port in the VLAN, whose VID is the current PVID, are sent untagged. Frames sent in all other VLANs active on the port are sent tagged. 462 Dell PowerConnect 55xx Systems User Guide