I have Pi-hole running on a Raspberry Pi 3 Model B+ with the latest Raspbian Stretch. This Pi-hole is connected to a Netgear BR500 router and is set to be both the DHCP and DNS server for the network. The router can assume or assign both DHCP and DNS server roles only together; i.e. it can't assume 1 of the 2 roles and assign the other.
I would like to assign the Raspberry Pi 3 Model B+ a new IP address. How do I go about this while minimizing connectivity disruptions to clients on the LAN?
I would do this in the middle of the night or whenever there are the fewest clients active on your network. Change the IP of the Pi, reconfigure Pi-Hole for the new IP using pihole -r (select reconfigure), then renew the DHCP lease on the clients.
If this will cause too much disruption, a more involved option would be to install a second Pi-Hole, configure the first Pi-Hole to assign clients the DNS address of both itself and the second Pi-Hole. Then, after the clients all have the DNS addresses of two Pi-Holes, you can shut the first one down and the clients will use the second during the time the first is down.
Many users run two Pi-Holes in parallel for redundancy - both for reliability reasons and the ability to take either one offline for maintenance, changes, etc, without affecting DNS resolution on their network.
OK thanks!