DGS-3700-12/DGS-3700-12G Series Layer 2 Gigabit Ethernet Switch User Manual
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VLAN and Trunk Groups
The members of a trunk group have the same VLAN setting. Any VLAN s etting on the member s of a trunk group will
apply to the other member ports.
NOTE: In order to use VLAN segmentation in conjunction with port trunk groups, you can first
set the port trunk group(s), and then you may configure VLAN settings. If you wish to change
the port trunk grouping with VLANs already in place, you will not need to reconfigure the VLAN
settings after changing the port trunk group settings. VLAN settings wil l autom atic all y change in
conjunction with the change of the port trunk group settings.
Double VLANs Double or Q-in-Q VLANs allow network providers to expand their VLAN configurations to place customer VLANs
within a larger inclusive VLAN, which adds a new layer to the VLAN configur ation. This basically lets large ISP's
create L2 Virtual Private Networks and also create transpare nt LANs for their custom ers, which will connec t two or
more customer LAN points without over-complicating configurations on the clien t's side. Not only will over-
complication be avoided, but also now the administrator has over 4000 VLANs in which over 4000 VLANs can be
placed, therefore greatly expanding the VLAN network and en abling greater support of custom ers utilizing multiple
VLANs on the network.
Double VLANs are basically VLAN tags placed within ex isting IEEE 802.1Q VLANs which we will call SPVIDs (Ser vice
Provider VLAN IDs). These VLANs are marked by a TPID (Tagged Protoco l ID), configured in hex form to be
encapsulated within the VLAN tag of the packet. This identifies the packet as double-tagged and segr egates it from
other VLANs on the network, therefore creating a hierarchy of VLANs with in a single packet.
Here is an example Double VLAN tagged packet.
Destination
Address Source
Address SPVLAN (TPID +
Service Provider
VLAN Tag)
802.1Q CEVLAN Tag
(TPID + Customer VLAN
Tag)
Ether
Type Payload
Consider the example below: