Dell PowerConnect B-FCXs Configuration Manual page 477

FIGURE 89
Untagged Packet Format
6 bytes
Destination
Address
6 bytes
Destination
Address
802.1q Tagged Packet Format
6 bytes
Destination
Address
6 bytes
Destination
Address
Octet 1
Tag Protocol Id (TPID)
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
configured across them. Notice that only one of the VLANs requires tagging.
PowerConnect B-Series FCX Configuration Guide
53-1002266-01
Packet containing a Dell 802.1Q VLAN tag
6 bytes 2 bytes
Source Type
Address Field
6 bytes
2 bytes
Source
Length
Address
Field
4 bytes
2 bytes
6 bytes
802.1q
Type
Source
Tag
Address Field
4 bytes
6 bytes 2 bytes
802.1q
Source Length
Tag
Address Field
1 2 3 4 5 6 7 8
Octet 2
802.1p
VLAN ID (12 bits)
(3 bits)
shows an example of two devices that have the same Layer 2 port-based VLANs
Up to 1500 bytes 4 bytes
Data Field CRC
Up to 1496 bytes 4 bytes
CRC
Data Field
Up to 1500 bytes
Data Field
Up to 1496 bytes
Data Field
Octet 4
VLAN overview
Ethernet II
IEEE 802.3
4 bytes
Ethernet II with 802.1q tag
CRC
4 bytes
IEEE 802.3 with 802.1q tag
CRC
13
435