ZyXEL Communications XS3800-28, User Manual, Page: 449 / 789

Chapter 60 VLAN Stacking
XS3800-28 User’s Guide
449
C
HAPTER
60
VLAN Stacking
This chapter shows you how to configure VLAN stacking on your Switch. See the chapter on VLANs for
more background information on Virtual LANs (VLANs).
60.1 VLAN Stacking Overview
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 4094 VLAN groups with each group containing up to 4094 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.
60.1.1 VLAN Stacking Example
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.