Interlogix GE-DS-242-PoE - Manual (Page 73)

Chapter 4: Console Management
GE-DS-242-PoE Managed Ethernet Switch User Manual 69
802.1Q VLAN
IEEE 802.1Q Tunneling (Q-in-Q)
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.
The Managed Switch supports multiple VLAN tags and can therefore be used in
MAN applications as a provider bridge, aggregating traffic from numerous
independent customer LANs into the MAN (Metro Access Network) space. One
of the purposes of the provider bridge is to recognize and use VLAN tags so that
the VLANs in the MAN space can be used independent of the customers' VLANs.
This is accomplished by adding a VLAN tag with a MAN-related VID for frames
entering the MAN. When leaving the MAN, the tag is stripped and the original
VLAN tag with the customer-related VID is again available.
This provides a tunneling mechanism to connect remote costumer VLANs
through a common MAN space without interfering with the VLAN tags. All tags