1. Navigate to Interfaces | Assignments, and click on the VLANs tab.
2. Click on the Add button.
3. Choose a Parent Interface from the drop-down menu; this should be a currently unassigned interface:

4. Enter a VLAN Tag from 2 to 4094 (1 is reserved as the default VLAN tag and should not be used).
5. Enter a VLAN Priority level from 0 to 7 (or just leave it at the default value of 0).
6. Enter a brief Description.
7. When you are done, click on the Save button.
8. Click on the Interface Assignments tab.
9. In the Available network ports column, select the newly created VLAN in the drop-down box, and click on the Add button:

10. To configure the VLAN, click on the interface name in the Interface column.
11. On the Interfaces configuration page, check the Enable Interface checkbox.
12. Change the Description to an appropriate one for the VLAN (for example, DEV).
13. Set the IPv4 Configuration Type to an appropriate value (usually Static IPv4).
14. Set the IPv6 Configuration Type, or leave it set to None.
15. If you set the IPv4 Configuration Type to Static IPv4, you must enter the IPv4 Address and CIDR for the new VLAN. Use a subnet that has not yet been used (for example, 192.168.10.1/24).

16. Leave the IPv4 Upstream gateway set to None.
17. If you set the IPv6 Configuration Type to Static IPv6, you must enter the IPv6 Address and CIDR for the new VLAN.
18. Leave the IPv6 Upstream gateway set to none.
19. Leave the Block private networks and Block bogon networks checkboxes unchecked.
20. When you are done making changes, click on the Save button, and then, when the page reloads, click on the Apply Changes button.