ZyXEL Communications Dimension ES-3124, User Manual

Page: 151 / 228

Dimension ES-3124 Ethernet Switch
VLAN Stacking 21-1
This chapter shows you how to configure VLAN stacking on your ES-3124. See the chapter on VLANs
for more background information on Virtual LAN
21.1 Introduction
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.
21.1.1 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.
Chapter 21
VLAN Stacking