How to Configure ASUSWRT-Merlin with DHCP Option 66
DHCP option 66 is useful for a VoIP phone to be automatically configured from a factory default state. DHCP will give the phone option 66, which points to the phone’s provisioning server.
Overview
DHCP option 66 is useful for a VoIP phone to be automatically configured from a factory default state. DHCP will give the phone option 66, which points to the phone’s provisioning server. The phone can then contact the server to download its configuration or upgrade its firmware.
ASUSWRT-Merlin is an open-source fork of ASUSWRT stock firmware.
Configuration
Web GUI
First, these options must be enabled from the Web GUI
Administration > System > Enable JFFS partition > Yes
Administration > System > Format JFFS partition at next boot > No
Administration > System > Enable SSH > Yes
SSH
Next, SSH into the router and open the jffs/configs directory
cd /jffs/configs
Create/edit dnsmasq.conf.add with vi text editor
vi dnsmasq.conf.add
Enter your DHCP Option 66 into dnsmasq.conf
dhcp-option=66,"http://sub.yourdomain.com"
Save that (ESC, :wq, ENTER), then reload dnsmasq
service restart_dnsmasq