Simultaneous support for tagged and untagged VLANs

Every interface is an untagged member of default VLAN or any user specified VLAN, unless user explicitly removes this untagged interface from default VLAN. The interface will always remain in the default VLAN (or non-default VLAN in which the interface is configured as untagged member), when this interface is added as tagged member of non-default VLAN. Thus, all tagged interfaces are implicit dual-mode ports.

This implicit dual-mode feature simplifies the tagging concept by changing the system default behavior to allow both tagged and untagged frames simultaneously (as per configurations). The dual-mode keyword is now deprecated, thus eliminating the need of explicit dual-mode configuration.

Note: With the introduction of implicit dual mode, CCEP ports cannot be configured as untagged member of default VLAN, when the default VLAN is a non MCT VLAN. Hence, the dual-mode configuration is disabled on CCEP ports as part of the image upgrade to current release.

ICX7250-24 Router(config)#vlan 100
ICX7250-24 Router(config-vlan-100)#tagged ethe 1/1/1
Added tagged port(s) ethe 1/1/1 to port-vlan 100.
ICX7250-24 Router(config-vlan-100)#vlan 1
ICX7250-24 Router(config-vlan-1)#no untagged ethe 1/1/1

Since user is allowed to remove ports from default VLAN which completely removes the untagged VLAN membership of an interface, this will be saved to running configuration to retain the VLAN membership upon reload. User VLANs will continue to display membership as per user configurations.

ICX7250-24 Router(config)#vlan 100
ICX7250-24 Router(config-vlan-100)#untagged ethe 1/1/1
Added untagged port(s) ethe 1/1/1 to port-vlan 100.
ICX7250-24 Router(config-vlan-100)#vlan 101
ICX7250-24 Router(config-vlan-1)#tagged ethe 1/1/2 to 1/1/3
ICX7250-24 Router(config-vlan-100)#vlan 1
ICX7250-24 Router(config-vlan-1)#no untagged ethe 1/1/2 to 1/1/3
ICX7250-24 Router(config-vlan-1)#sh ru vlan
vlan 1 name DEFAULT-VLAN by port
no untagged ethe 1/1/2 to 1/1/3***
vlan 100 by port
 untagged ethe 1/1/1 
As you can see, only the interfaces that are deleted explicitly by the user is displayed. If an interface is moved internally as part of some other VLAN configurations (1/1/1, in the above example), it is not displayed under default-VLAN.
Note: Show VLAN output will no more display dual-mode and uplink ports. This command displays VLAN membership as per the option provided. There is no change in VLAN display order, but default VLAN displays the interfaces that are explicitly removed from default VLAN using the no untagged ethernet command.