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Chapter 23 VLAN Stacking
MGS3700-12C User’s Guide
233
23.3 VLAN Tag Format
A VLAN tag (service provider VLAN stacking or customer IEEE 802.1Q) consists of
the following three fields.
TPID (Tag Protocol Identifier) is a standard Ethernet type code identifying the
frame and indicates that whether the frame carries IEEE 802.1Q tag information.
The value of this field is 0x8100 as defined in IEEE 802.1Q. Other vendors may
use a different value, such as 0x9100.
Tunnel TPID is the VLAN stacking tag type the Switch adds to the outgoing
frames sent through a Tunnel Port of the service provider's edge devices (1 and
2 in the VLAN stacking example figure).
Priority refers to the IEEE 802.1p standard that allows the service provider to
prioritize traffic based on the class of service (CoS) the customer has paid for.
• On the Switch, configure priority level of inner IEEE 802.1Q tag in the Port
Setup screen.
• "0" is the lowest priority level and "7" is the highest.
VID is the VLAN ID. SP VID is the VID for the second (service provider’s) VLAN
tag.
23.3.1 Frame Format
The frame format for an untagged Ethernet frame, a single-tagged 802.1Q frame
(customer) and a “double-tagged” 802.1Q frame (service provider) is shown next.
Configure the fields as highlighted in the Switch VLAN Stacking screen.
Table 60 VLAN Tag Format
TPID Priority VID
Table 61 Single and Double Tagged 802.11Q Frame Format
DA SA Len/
Etype
Dat
a
FCS Untagged
Ethernet
frame
DA SA TPI
D
Priorit
y
VI
D
Len/
Etype
Dat
a
FCS
IEEE 802.1Q
customer
tagged
frame
D
A
SA Tunne
l TPID
Priori
ty
VI
D
TPI
D
Priorit
y
VI
D
Len/
Etype
Dat
a
FCS
Double-
tagged
frame