If you are using a Shoretel IP phone system, you need to ensure that you add option 156 to your DHCP settings so that your handsets know which options to use, like FTP Server and VLANs.
But, option 156 is not a default option you can add in DHCP so you need to manually add it in and then you can use it to setup your options.
To do this, open up the DHCP console on your server and do the following steps:
- Right-click IPv4 and select Set Predefined Options
- Click Add and in the Name field
- Type IP Phones (or similar identifier)
- Set the Data type to String
- Enter the Code type as 156