Introduction

Below are the steps needed to setup PiHole with Unifi UDM Pro. The sofware versions involved are:

• Unifi UDM Pro: Network v6.5.55
• Raspberry PI 4: PiHole v5.8.1

TL;DR

The main actions to note are:

• Setup networks for devices that you require in Unifi.
• Ensure the networks have no content filtering in Unifi.
• Setup appropriate network/firewall rules to allow access to DNS.
• Install and enable PiHole

Configuration

PiHole

I have a raspberry Pi 4 attached to my home network.

• Configure & install raspbery Pi on your device: https://www.raspberrypi.com/software/ make sure SSH is enabled.
• Install PiHole https://docs.pi-hole.net/main/basic-install/
• If you have several networks/subnets set up you'll need to Permit all origins
• Go to settings -> DNS -> Interface Settings
• 
• Save those changes.

Unifi

I have setup 4 networks with the following CIDRs: Unifi network CIDRs

You need to setup firewall rules to control traffic on your network but in order to allow DNS traffic to your PiHole you'll need the following:

• Rule Type: LAN in
• Description: ALLOW ALL to DNS
• Action: Accept
• IPv4 Protocol: TCP and UDP

Source Settings

• Source Type: Address/Port Group
• IPv4 Address Group: Any
• IPv4 Port Group: Any

Destination Settings

• Destination Type: Address/Port Group
• IPv4 Protocol: DNS Server -> Create a group with the IP of the DNS Server with PiHole.
• Port Group: DNS Port -> Create a group with the port number 53.

Save those settings.

Next you'll need to set the DNS IP for all the networks that you've setup as follows: Go to each network and set the DNS IP to the DNS Server (in my case it's 192.168.1.2):

Make sure that no content filtering settings have been set as this will interfere with DNS queries.

Save those settings.