Brocade Multi-Service IronWare Switching Configuration Guide (Supporting R05.6.00) - Manual (Page 199)

Multi-Service IronWare Switching Configuration Guide 169
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VLAN configuration rules
7
When the no untagged ethernet <slot-number> / <port-number> command is applied under the
default VLAN against a port in dual mode, the port will go into pure tagged mode in contrast to the
default operating conditions where the port is automatically placed in the dual mode state with
regard to the default VLAN. To change the default condition of a Brocade device regarding the
dual-mode, default VLAN behavior, enter the no dual-mode-default-vlan command as shown in the
following.
Brocade(config)# no dual-mode-default-vlan
Syntax: [no] dual-mode-default-vlan
The default state is for ports added as tagged to a non-default VLAN to remain as untagged ports in
the default VLAN and become dual-mode ports.
Using this command with the no option, changes the default state and automatically removes a
port from the default VLAN when it is added as a tagged port to a non-default VLAN. Using the
command without the no option, will return the systems behavior to its normal operating condition.
NOTE
When a Brocade device is operating in the default state regarding the no dual-mode-default-vlan
command (which is not configured), syslog messages are generated whenever a port is moved out
of the default VLAN. This is normal and expected behavior. Because when the no
dual-mode-default-vlan command is configured, it is normal operating behavior for a port to be
moved out of the default VLAN whenever it enters the dual-mode state syslog messages may be
generated when the ports are moved, which is not expected. These messages may be generated in
the following situations:
• When a port is added “tagged” into the default VLAN, it is automatically deleted from the
default VLAN and a syslog message is generated.
• When a port is in dual-mode, and a user issues the no untagged port-no command within the
port VLAN configuration, the port is added back to the default VLAN. However, because the no
dual-mode-default-vlan command is configured, the port is transitioned out of the default
VLAN which generates an additional syslog message.
Restrictions for use of this command
The no dual-mode-default-vlan command can only be applied if the device does not currently have
any ports configured in dual-mode. If any port is currently in the dual-mode state when the no
dual-mode-default-vlan command is executed, the command is rejected without it being applied to
any ports on the device. Consequently, using the no dual-mode-default-vlan command does not
cause any action but enables a new behavior for ports that are added to a VLAN.
If there are ports configured into the dual-mode (default VLAN) state, they can be moved from that
state by removing untagged ports the default VLAN that also exist as tagged in a non-default VLAN
or removing tagged ports from the non-default VLANs.
Disabling dual-mode for tagged ports
Unless you have a specific need to operate a tagged port in dual-mode, you should make it strictly
tagged by removing it from the set of untagged ports in the default VLAN.