Install Adblock in your OpenWRT Router OS

 Adblock software in OpenWRT is a script running in your OpenWRT gateway to sort out those DNS queries that ask for the resources recrds of ad servers and return a simple 'NSDOMAIN'. This action will make your browser not able to show those ads on the page you are surfing. 

Topology

A simple topology to show you the position of OpenWRT Virtual machines I installed in VMWare Workstation. It is inside my Windows 2016 host connecting to a giga switch. Other devices in my home network, they are either connecting through WiFi or through wired connection to switch. 

Prerequisites

• OpenWrt, tested with the stable release series (19.07.x) and with the latest rolling snapshot releases. On turris devices it has been successfully tested with TurrisOS 5.1.x
• A download utility with SSL support: 'wget', 'uclient-fetch' with one of the 'libustream-*' ssl libraries, 'aria2c' or 'curl' is required
• Option: DNS Reporting, TCPDUMP or TCPDUMP-Mini installed
• Client DNS pointing to OpenWRT

Installation Steps

From OpenWRT Luci Web GUI:

• Click Update Lists from OpenWRT Web GUI - System - Software

• Install adblock and luci-app-adblock
• Install wget / Curl 
• Reboot OpenWRT
• Browse to OpenWRT Web GUI - Services - Adblock

From Console or SSH Session:

• Update your local opkg repository (opkg update)
• Install 'adblock' (opkg install adblock). The adblock service is enabled by default
• Install the LuCI companion package 'luci-app-adblock' (opkg install luci-app-adblock)
• It's strongly recommended to use the LuCI frontend to easily configure all aspects of adblock, the application is located in LuCI under the 'Services' menu
• Update from a former adblock version is easy. During the update a backup is made of the old configuration '/etc/config/adblock-backup' and replaced by the new config - that's all

References

• OpenWRT Wiki - Ad blocking
• DNS based ad/abuse domain blocking
• Layman's guide for Adblock (on WRT1900AC)