There are many ways to upgrade your Grandstream device firmware. DHCP Option 66 is a great way to upgrade Grandstream device firmware (and many other brands) without having to login to the devices web interface and manually set the firmware server path. This allows you to upgrade Grandstream device firmware automatically from an out of the box state and can also be used for scheduled upgrades if the device has been configured to do so.

The example below shows you how to setup DHCP Option 66 on a MikroTik DHCP server although you can configure DHCP Options on other servers (i.e. Microsoft Windows and Linux DHCP Servers).

Create a new DHCP Option 66 and it to your DHCP Network:

Name: Can be anything to identify your DHCP Option

Code: 66

Value: ''

DHCP Discover is the first message in a DHCP Request. The client device (00:0b:82:f9:ae:32) sends a broadcast message to the network in hope a DHCP Server will respond with a DHCP Offer:

The DHCP Server then responds with a DHCP Offer to the client devices broadcast message:

The client device then sends a DHCP Request, requesting the IP Address which has been offered be allocated/reserved to the client device ( The client device also requests a list of configuration parameters (Option 50) which includes our Option 66 (TFTP Server Name):

The Server then responds with a DHCP Acknowledgement which includes the clients requested parameter information (Option 66 TFTP Server Name Value), Lease time and other relevant DHCP information.