I am running two Raspberry Pis, with Nebula Sync updating the secondary one. My primary Pi is also acting as a DHCP server, using Pi Hole’s DHCP server.
When I set up Nebula Sync, I configured it to NOT do a full sync, and to not sync DHCP. My experience in IT has taught me that more than one DHCP server is bad… usually.
With Pi Hole, is there any reason do not do a full sync, and let both devices serve DHCP? Or is a single DHCP server still best practice?
Thank you for the sanity check!
Just like with other DHCP servers, you should have just one DHCP server on a specific IP range.
If both servers are giving IP addresses in the same range, how would they avoid to assign the same IP to different devices, to avoid collisions?
You can have multiple DHCP servers if they are assigning different ranges. Example:
192.168.0.10-192.168.0.100192.168.0.110-192.168.0.200I'd say always. Unless you have something along the lines of HSRP, the problem is going to be that DHCP is a broadcast technology and there's nothing to dictate which server is going to reply to the 255.255.255.255 request packet from the clients.
You could sync the databases so that both Pi-hole servers know the names of the clients if they register their names with the lease requests and if you use those names on the LAN in place of their IPs for services.
Multiple DHCP servers is possible but it would require some software or hardware in front of the two servers that is not part of Pi-hole.
OK, that answers my question. The end goal was just to do a Full Sync from Primary to Secondary to de-complicate things, but it looks like that Full Sync would overlap the DHCP scope and cause potential conflicts.
So the answer is not to do a full sync, and let the primary handle DHCP - I can enable it on the second in an emergency if needed.
Thank you for the insight!
Get yourself two Intel N100 Mini PCs with a Quad Port Intel NIC and install OPNsense on them : Dnsmasq DNS & DHCP — OPNsense documentation 
How does that fix this issue?
It was meant in the spirit of “If you want true High Availability for your network” so to speak
Not saying he MUST DO IT but it’s something to think about! 