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MGS3700-12C User’s Guide
231
CHAPTER 23
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 LAN
23.1 VLAN Stacking Overview
A service provider can use VLAN stacking (also known as Q-in-Q) 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.
23.1.1 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