User's Manual

21-24
Chapter 21 Flexible Q-in-Q Configuration
21.1 Introduction to Flexible Q-in-Q
21.1.1 Q-in-Q Technique
Dot1q-tunnel is also called Q-in-Q (802.1Q-in-802.1Q), which is an expansion of 802.1Q. Its dominating idea
is encapsulating the customer VLAN tag (CVLAN tag) to the service provider VLAN tag (SPVLAN tag). The
packet with two VLAN tags is transmitted through the backbone network of the ISP internet to provide a
simple layer-2 tunnel for the users. It is simple and easy to manage, applicable only by static configuration,
and especially adaptive to small office network or small metropolitan area network using layer-3 switch as
backbone equipment.
There are two kinds of Q-in-Q: basic Q-in-Q and flexible Q-in-Q, the priority of flexible Q-in-Q is higher than
basic Q-in-Q.
21.1.2 Basic Q-in-Q
Basic Q-in-Q based the port. After a port configures Q-in-Q, whether the received packet with tag or not, the
device still packs the default VLAN tag for the packet. Using basic Q-in-Q is simple, but the setting method of
VLAN tag is inflexible.
21.1.3 Flexible Q-in-Q
Flexible Q-in-Q based data flow. It selects whether pack the external tag and packs what kind of the external
tag by matching the material flow. For example: implement the property of flexible Q-in-Q according to the
user’s VLAN tag, MAC address, IPv4/IPv6 address, IPv4/IPv6 protocol and the port ID of the application, etc.
So, it can encapsulate the external tag for the packet and implements different scheme by different users or
methods.
21.2 Flexible Q-in-Q Configuration Task List
The match of flexible Q-in-Q data flow uses policy-map rule of QoS to be sent, the configuration task list is as
follows:
1. Create class-map to classify different data flows
2. Create flexible Q-in-Q policy-map to relate with the class-map and set the corresponding operation
3. Bind flexible Q-in-Q policy-map to port