RUGGEDCOM ROS
User Guide
Chapter 5
Setup and Configuration
QinQ
139
The outer tag VID is the PVID of the frame's ingress edge port. This means that traffic from an individual customer
is tagged with their unique VID and is thus segregated from other customer's traffic. For untagged ingress frames,
the switch will only add the outer VLAN tag.
Within the service provider network, switching is based on the VID in the outer tag.
When double-tagged frames leave the service provider network, they egress a QinQ-enabled port of another
switch. The switch strips the outer tag while associating the frames with the VID extracted from it before stripping.
Thus, the frames are switched to appropriate edge ports ( i.e. customers).
The following figure shows an example of traffic flow using QinQ.
For tagged frames:
• Frames received from customer 1 with VID 100 would carry an inner tag of 100 and an outer tag of VID X (i.e.
VLAN 110) which is configured on the edge port connected to customer 1.
• Next, the frames from customer 1 are forwarded through the QinQ port carrying an inner and an outer tag.
• Finally, upon arrival of the frames in the peer switch, the outer VLAN tag is removed and the frames are
forwarded with the inner VLAN tag towards customer 1.
For untagged frames:
• Frames received from customer 2 would carry an outer tag of VID Y(i.e VLAN 220) which is configured on the
edge port connected to customer 2.
• Next, the frames from customer 2 are forwarded through the QinQ port carrying the outer tag.
• Finally, upon arrival of the frames in the peer switch, the outer VLAN tag is removed before the frames are
forwarded to customer 2.
1
5
2
3
5
1
4
2
4
Figure 78: Using QinQ
1.
Customer 1 (PVID is X)
2.
Customer 2 (PVID is Y)
3.
Network Service Provider Infrastructure
4.
Switch
5.
QinQ
NOTE
Depending on the hardware installed, some switch models allow only one switch port be configured to
QinQ mode at a time.
NOTE
When QinQ is enabled, all non-QinQ ports will be untagged and cannot be changed, and all QinQ ports
will be tagged, and cannot be changed.
