Dell PowerConnect FCS624S Configuration Guide - Page 477

VLAN overview 13 FIGURE 89 Packet containing a Dell 802.1Q VLAN tag Untagged Packet Format 6 bytes Destination Address 6 bytes Source Address 2 bytes Type Field 6 bytes Destination Address 6 bytes Source Address 2 bytes Length Field Up to 1500 bytes Data Field Up to 1496 bytes Data Field 4 bytes CRC Ethernet II 4 bytes CRC IEEE 802.3 802.1q Tagged Packet Format 6 bytes Destination Address 6 bytes Destination Address 6 bytes Source Address 6 bytes Source Address 4 bytes 802.1q Tag 4 bytes 802.1q Tag 2 bytes Type Field 2 bytes Length Field Up to 1500 bytes Data Field Up to 1496 bytes Data Field 4 bytes Ethernet II with 802.1q tag CRC 4 bytes CRC IEEE 802.3 with 802.1q tag Octet 1 Octet 2 12 3456 78 Octet 4 Tag Protocol Id (TPID) 802.1p (3 bits) VLAN ID (12 bits) If you configure a VLAN that spans multiple devices, you need to use tagging only if a port connecting one of the devices to the other is a member of more than one port-based VLAN. If a port connecting one device to the other is a member of only a single port-based VLAN, tagging is not required. If you use tagging on multiple devices, each device must be configured for tagging and must use the same tag value. In addition, the implementation of tagging must be compatible on the devices. The tagging on all Dell PowerConnect devices is compatible with other Dell PowerConnect devices. Figure 90 shows an example of two devices that have the same Layer 2 port-based VLANs configured across them. Notice that only one of the VLANs requires tagging. PowerConnect B-Series FCX Configuration Guide 435 53-1002266-01