Chapter 21 VLAN Stacking
GS3700/XGS3700 Series User’s Guide
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Type is a standard Ethernet type code identifying the frame and indicates that whether the frame
carries IEEE 802.1Q tag information. SP TPID (Service Provider Tag Protocol Identifier) is the
service provider VLAN stacking tag type. Many vendors use 0x8100 or 0x9100.
TPID (Tag Protocol Identifier) is the customer IEEE 802.1Q tag.
• If the VLAN stacking port role is Access Port, then the Switch adds the SP TPID tag to all
incoming frames on the service provider's edge devices (1 and 2 in the VLAN stacking example
figure).
• If the VLAN stacking port role is Tunnel Port, then the Switch only adds the SP TPID tag to all
incoming frames on the service provider's edge devices (1 and 2 in the VLAN stacking example
figure) that have an SP TPID different to the one configured on the Switch. (If an incoming
frame’s SP TPID is the same as the one configured on the Switch, then the Switch will not add
the tag.)
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 the 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.
21.3.1 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.
21.4 Configuring VLAN Stacking
Click Advanced Application > VLAN Stacking to display the screen as shown.
Table 78
Single and Double Tagged 802.11Q Frame Format
DA
SA
Len/Etype
Data
FCS
Untagged
Ethernet frame
DA
SA
TPID Priority
VID Len/Etype
Data
FCS
IEEE 802.1Q
customer
tagged frame
DA
SA
SPTPID
Priority VID
TPID Priority VID
Len/Etype
Data
FCS
Double-tagged
frame
Table 79
802.1Q Frame
DA
Destination Address
Priority
802.1p Priority
SA
Source Address
Len/Etype
Length and type of Ethernet frame
(SP)TPID
(Service Provider) Tag Protocol IDentifier
Data
Frame data
VID
VLAN ID
FCS
Frame Check Sequence
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