Brocade Virtual ADX Switch and Router Guide (Supporting ADX v03.1.00) - Manual (Page 40)

26 Brocade Virtual ADX Switch and Router Guide
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Overview
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FIGURE 2 Default Layer 2 port-based VLAN
When you configure a port-based VLAN, one of the configuration items you provide is the ports that
are in the VLAN. When you configure the VLAN, the Virtual ADX automatically removes the ports
that you place in the VLAN from DEFAULT-VLAN. By removing the ports from the default VLAN, the
Virtual ADX ensures that each port resides in only one Layer 2 broadcast domain.
NOTE
Information for the default VLAN is available only after you define another VLAN.
Some network configurations may require that a port be able to reside in two or more Layer 2
broadcast domains (port-based VLANs). In this case, you can enable a port to reside in multiple
port-based VLANs by tagging the port. See the following section.
If your network requires that you use VLAN ID 1 for a user-configured VLAN, you can reassign the
default VLAN to another valid VLAN ID. Refer to
“Assigning a different VLAN ID to the default VLAN”
on page 34.
802.1q tagging
802.1q tagging is an IEEE standard that allows a networking device to add information to a Layer 2
packet in order to identify the VLAN membership of the packet. A Virtual ADX tags a packet by
adding a four-byte tag to the packet. The tag contains the tag value, which identifies the data as a
tag, and also contains the VLAN ID of the VLAN from which the packet is sent.
The tag contains the following: