Group VLAN Assignment Window

This window appears when you select a port or VLAN and click Modify in the VLAN Membership window. Use it to complete these tasks:

Assigning Static-Access Ports to VLANs

To assign static-access ports to a different VLAN:

  1. Select Static Access from the Mode list.
    Remember that static-access ports can belong to only one VLAN.
  2. To assign the ports that you selected to a different VLAN, enter the VLAN ID.
    Valid entries range from 1 to 1001.
    Note: If you change the VLAN ID on a port in a EtherChannel port group, the ID for all ports in the group also changes.
  3. Click OK to put your changes in effect.

Assigning Dynamic-Access Ports to VLANs

To assign a dynamic-access port to a VLAN:

  1. Select Dynamic Access from the Mode list.
    Because the VMPS assigns VLAN numbers to dynamic-access ports, the VLAN ID field in this window changes to read-only.
  2. Click OK to put your changes in effect.

Assigning Multi-VLAN Ports to VLANs

To assign a multi-VLAN port to a VLAN:

  1. Select Multi-VLAN from the Mode list.
  2. In the VLAN ID field, enter the VLANs in which this port will be a member.
    Valid entries range from 1 to 1001. To enter multiple VLAN IDs, enter a comma between ID numbers or enter a hyphen (-) between ID numbers to specify a VLAN range.
  3. Click OK to put your changes in effect

Configuring a Trunk Port

To configure a trunk port:

  1. Click the Assign VLAN tab on the VLAN Membership window.
  2. Select the port to serve as the trunk port.
  3. Click Modify to display the Group VLAN Assignment window.
  4. Select ISL or 802.1Q  from the VLAN Mode list.
    Because the port is automatically assigned to all active VLANs in the VTP domain, the Assigned VLANs field becomes read-only. To restrict VLAN membership for this port, see Specifying Allowed VLANs.
    Note: If you configured an 802.1Q trunk, see Special 802.1Q Trunk Considerations.
  5. Click OK to create the trunk and to close the Group VLAN Assignment window.
    The trunk port appears on the Assign VLANs tab.
    Note: If this switch is in a VTP domain, see Disabling Pruning for changes you might need to make on the new trunk.
  6. Click OK to close the VLAN Membership window.

Special 802.1Q Trunk Considerations. The Per VLAN Spanning Tree+ (PVST+) protocol is automatically enabled on 802.1Q trunks. This protocol ensures interoperability between Cisco devices that implement one spanning-tree instance per VLAN (PVST) and devices that implement one spanning tree for all VLANs in the network (specified in the IEEE 802.1 standard). By default, the switch forwards untagged traffic with the native VLAN configured for the port.

Disabling STP on the native VLAN of an 802.1Q trunk or disabling STP on any VLAN in the network can cause STP loops. Cisco recommends that you leave STP enabled on the native VLAN of an 802.1Q trunk, or disable STP on every VLAN in the network (see Configuring Spanning Tree Protocol).

Specifying Allowed VLANs

To restrict the VLAN membership for a trunk port:

  1. In the Allowed VLAN List section, enter the IDs of VLANs for which the port will forward traffic.
  2. Click OK to put your change in effect.

Disabling Pruning

To remove a VLAN from the Pruning Eligibility list:

  1. In the VLAN Pruning Eligibility list, enter the VLAN number in the VLAN ID field.
  2. Click OK to put your change in effect.