ZyXEL Communications 4528F User Manual

XGS-4526/4528F/4728F User’s Guide

This chapter shows you how to configure VLAN stacking on your Switch. See the 
chapter on VLANs for more background information on Virtual LAN

A service provider can use VLAN stacking to allow it to distinguish multiple 
customers VLANs, even those with the same (customer-assigned) VLAN ID, within 
its network.

Use VLAN stacking 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 service, 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 
on ports for these applications. 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. 

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