SMC Networks TigerAccess SMC7816M - Manual (Page 354)

VLAN C
ONFIGURATION
13-24
Configuring IEEE 802.1Q Tunneling
IEEE 802.1Q Tunneling (QinQ) is designed for service providers carrying
traffic for multiple customers across their networks. QinQ tunneling is
used to maintain customer-specific VLAN and Layer 2 protocol
configurations even when different customers use the same internal
VLAN IDs. This is accomplished by inserting Service Provider VLAN
(SPVLAN) tags into the customer’s frames when they enter the service
provider’s network, and then stripping the tags when the frames leave the
network.
A service provider’s customers may have specific requirements for their
internal VLAN IDs and number of VLANs supported. VLAN ranges
required by different customers in the same service-provider network
might easily overlap, and traffic passing through the infrastructure might
be mixed. Assigning a unique range of VLAN IDs to each customer would
restrict customer configurations, require intensive processing of VLAN
mapping tables, and could easily exceed the maximum VLAN limit of
4096.
QinQ tunneling uses a single Service Provider VLAN (SPVLAN) for
customers who have multiple VLANs. Customer VLAN IDs are preserved
and traffic from different customers is segregated within the service
provider’s network even when they use the same customer-specific VLAN
IDs. QinQ tunneling expands VLAN space by using a VLAN-in-VLAN
hierarchy, preserving the customer’s original tagged packets, and adding
SPVLAN tags to each frame (also called double tagging).
A port configured to support QinQ tunneling must be set to tunnel port
mode. The Service Provider VLAN (SPVLAN) ID for the specific
customer must be assigned to the QinQ tunnel port on the edge switch
where the customer traffic enters the service provider’s network. Each
customer requires a separate SPVLAN, but this VLAN will support all of
the customer's internal VLANs. The QinQ uplink port that passes traffic
from the edge switch into the service provider’s metro network must also