ZyXEL Communications IES-612-51A User Manual

IES-612-51A User’s Guide

This chapter shows you how to set up Transparent LAN Service (VLAN stacking, Q-in-Q) on 
each port.

Transparent LAN Service (also known as VLAN stacking or Q-in-Q) allows a service provider 
to distinguish multiple customers VLANs, even those with the same (customer-assigned) 
VLAN ID, within its network.

Use TLS to add an outer VLAN tag to the inner IEEE 802.1Q tagged frames that enter the 
network. By tagging the tagged frames (“double-tagged” frames), the service provider can 
manage up to 4,094 VLAN groups with each group containing up to 4,094 customer VLANs. 
This allows a service provider to provide different services, based on specific VLANs, for 
many different customers.

A service provider’s customers may require a range of VLANs to handle multiple 
applications. A service provider’s customers can assign their own inner VLAN tags to traffic. 
The service provider can assign an outer VLAN tag for each customer. Therefore, there is no 
VLAN tag overlap among customers, so traffic from different customers is kept separate.

Before the IES-612-51A sends the frames from the customers, the VLAN ID is added to the 
frames. When packets intended for specific customers are received on the IES-612-51A, the 
outer VLAN tag is removed before the traffic is sent.

In the following example figure, both A and B are Service Provider’s Network (SPN) 
customers with VPN tunnels between their head offices and branch offices, respectively. Both 
have an identical VLAN tag for their VLAN group. The service provider can separate these 
two VLANs within its network by adding tag 37 to distinguish customer A and tag 48 to 
distinguish customer B at edge device 1 and then stripping those tags at edge device 2 as the 
data frames leave the network.