Dell PowerConnect B-RX Configuration Manual page 364

11
Overview of Virtual Local Area Networks (VLANs)
FIGURE 21
Destination
802.1q Tagged Packet Format
Destination
Destination
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 devices is compatible with other Brocade devices.
Figure 22
configured across them. Notice that only one of the VLANs requires tagging.
288
Packet containing Brocade's 802.1QVLAN tag
Untagged Packet Format
6 bytes 2 bytes
6 bytes
Source Type
Address Field
Address
6 bytes 6 bytes
2 bytes
Destination Source
Length
Address Address
Field
6 bytes 4 bytes
6 bytes
802.1q
Source
Tag
Address
Address
4 bytes
6 bytes 6 bytes
802.1q
Source
Tag
Address Address
Octet 1 1 2 3 4 5 6 7 8
Octet 2
802.1p
Tag Protocol Id (TPID)
(3 bits)
shows an example of two devices that have the same Layer 2 port-based VLANs
Up to 1500 bytes
Data Field
Up to 1496 bytes
Data Field
2 bytes
Up to 1500 bytes
Type
Data Field
Field
2 bytes
Up to 1496 bytes
Length
Data Field
Field
Octet 4
VLAN ID (12 bits)
4 bytes
Ethernet II
CRC
4 bytes
IEEE 802.3
CRC
4 bytes
Ethernet II with 802.1q tag
CRC
4 bytes
IEEE 802.3 with 802.1q tag
CRC
BigIron RX Series Configuration Guide
53-1002253-01