ZyXEL XGS4700-48F User Guide - Page 223

Chapter 23 VLAN Stacking 23.3 VLAN Tag Format A VLAN tag (service provider VLAN stacking or customer IEEE 802.1Q) consists of the following three fields. Table 56 VLAN Tag Format Type Priority VID 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. 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. XGS4700-48F User's Guide 223