Brocade Virtual ADX Switch and Router Guide (Supporting ADX v03.1.00) - Manual (Page 41)

Brocade Virtual ADX Switch and Router Guide 27
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Overview
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• The default tag value is 8100 (hexadecimal). This value comes from the 802.1q specification.
You can change this tag value on a global basis on a Virtual ADX if needed to be compatible
with other vendors’ equipment.
• The VLAN ID is determined by the VLAN on which the packet is being forwarded.
Figure 3 shows the format of packets with and without the 802.1q tag. The tag format is
vendor-specific. To use the tag for VLANs configured across multiple devices, make sure all the
devices support the same tag format.
FIGURE 3 Packet containing an 802.1QVLAN tag
NOTE
You cannot configure a port to be a member of the default port-based VLAN and another port-based
VLAN at the same time. Once you add a port to a port-based VLAN, the port is no longer a member
of the default VLAN. The port returns to the default VLAN only if you delete the other VLANs that
contains the port.
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 Brocade devices is compatible with other Brocade devices.
Figure 4 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.