xStack® DGS-3120 Series Managed Switch Web UI Reference Guide
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more customer LAN points without over-complicating configurations on the client'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 enabling greater support of customers utilizing multiple
VLANs on the network.
Double VLANs are basically VLAN tags placed within existing IEEE 802.1Q VLANs which we will call SPVIDs
(Service Provider VLAN IDs). These VLANs are marked by a TPID (Tagged Protocol ID), configured in hex form to
be encapsulated within the VLAN tag of the packet. This identifies the packet as double-tagged and segregates it
from other VLANs on the network, therefore creating a hierarchy of VLANs within 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:
Figure 4–25 QinQ example window
In this example, the Service Provider Access Network switch (Provider edge switch) is the device creating and
configuring Double VLANs. Both CEVLANs (Customer VLANs), 10 and 11, are tagged with the SPVID 100 on the
Service Provider Access Network and therefore belong to one VLAN on the Service Provider’s network, thus being
a member of two VLANs. In this way, the Customer can retain its normal VLAN and the Service Provider can
congregate multiple Customer VLANs within one SPVLAN, thus greatly regulating traffic and routing on the Service
Provider switch. This information is then routed to the Service Provider’s main network and regarded there as one
VLAN, with one set of protocols and one routing behavior.
Some rules and regulations apply with the implementation of the Double VLAN procedure.
Regulations for Double VLANs
1. All ports must be configured for the SPVID and its corresponding TPID on the Service Provider’s edge
switch.
Summary of Contents for xStack DGS-3120-24TC
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