Running two Pi-Holes at the same time / Replacement + Setup

Help
1

I want to rebuild my pi.hole on a new, separate RasPi 4.

  • Since the new pi.hole will use different IP addresses as the currently running one, I should be able to set it up while the current pi.hole on the RasPi 3 is still running and serving DNS requests during the setup and configuration phase of the new pi.hole on RasPi 4.

  • There will be no conflicts by doing so? Except I need to SSH to the IP address or hostname.

  • Since both devices will be avail at the the default pi.hole name, that's the only conflict I can think of while building the new one.

Once the new Pi-Hole at new IP v4+v6 is ready for use in the production system, I simply replace the DHCP propagated DNS Servers in the server to the newly build system?

Are these assumptions correct for the purpose of replacing the Pi-Hole Server device without conflicts?

2

Yes to the two first bullet items.
The third (pi.hole) could be addressed by configuring PIHOLE_PTR (available since FTL v5.10.1) on at least one of the machines, but wouldn't lead to immediate issues if left as is, apart from ambiguity when accessing Pi-hole's UI from the new device while both RPIs are active.

Yes, plus the equivalent for DHCPv6 and RAs, provided your router supports those IPv6 related configuration options.