Configuring Switching Information 343Double VLANThe Double VLAN feature allows the use of a second tag on network traffic. The additional tag helpsdifferentiate between customers in the Metropolitan Area Networks (MAN) while preserving individualcustomer’s VLAN identification when they enter their own 802.1Q domain.With the introduction of this second tag, you do not need to divide the 4k VLAN ID space to send trafficon an Ethernet-based MAN.With Double VLAN Tunneling enabled, every frame that is transmitted from an interface has a DVLANTag attached while every packet that is received from an interface has a tag removed (if one or more tagsare present).Use the Double VLAN Global Configuration page to specify the Double VLAN configuration for all theports.To access the Double VLAN Global Configuration page, click Switching →VLAN →Double VLAN →Global Configuration from the navigation tree.Table 7-26. VLAN Membership CommandsCLI Command Descriptionname Configures a name to a VLAN.show interfaces switchport Displays switchport configuration.show vlan Displays VLAN information.switchport forbidden vlan Forbids adding specific VLANs to a port.switchport general allowed vlan Adds or removes VLANs from a port in General mode.switchport trunk allowed vlan Adds or removes VLANs from a port in general mode.vlan Creates a VLAN.vlan database Enters the VLAN database configuration mode.vlan makestatic Changes a dynamically created VLAN to a static VLAN.
