Selfhosted

Generally speaking, any device ("server") hosting a "service" NEEDS to be assigned a static IP. It simplifies routing significantly and avoids random break problems because DHCP is incredibly stupid at times....

Is there any specific reason you need DHCP to assign an IP to your main hosting server vs setting it all statically?

Moving it to it's own system will not fix the routing problem. You can probably still leave it on the USG.

You should be able to set a fixed static IP on your server, and then also statically assign that same IP to your server in your USG DHCP config- as long as they both are "thinking about" the same IP I think routing should work correctly.

If that breaks, try just assigning the static IP only from the USG side or only from the server's side. I'm 90% sure that even if the USG does not have your server machine in it's client list, if it sends broadcast packets to an entered IP looking for the unifi server, and the unifi server is listening on that manually set IP, they should be able to talk.

disclaimer: i am high as shit right now and this may be bullshit

Either use a static IP on the server or setup DHCP to always reserve & assign a specific IP for the server's MAC address.

I'm not familiar with USG but any decent appliance with DHCP+DNS functionality should be able to do this.

Sidnenote about the PI filesystem self-clobbering: Are you running off of an SD card? Running off an external SSD is way more reliable in my experience. Even a decent USB stick tends to be better than micro-SD in the long run, but even the cheapest external SSD blows both of them out of the water. Since I switched my PIs over to that, they've never had any disk-related issues.

Basically, Unifi needs to know where the unifi server is, but it’s assigning the IP address to it.

Set a static IP on the Unifi server.

I use pihole for managing DNS and DHCP. It's run via docker and the compose file and dnsmasq configs are version controlled so if the Pi dies I can just bring it up on another Pi.

The Pi with pihole has a static IP to avoid some of the issues you described.

Unifi is specific about expecting the controller address to not change. You have several options: There's the “override controller address” setting, which you can use to point the devices at a dns name, instead of an ip address. The dns can then track your controller. It doesn’t exactly solve your issue, though, as USG doesn’t assign dns names to dynamic allocations.

Another option is to give the controller a static IP allocation. This way, in case you reboot everything, USG will come up with the latest good config, then will (eventually) allocate the IP for controller, and adopt itself.

Finally, the most bulletproof option is to just have a static IP address on the controller. It's a special case, so it's reasonable to do so. Just like you can only send NetFlow to a specific address and have to keep your collector in one place, basically.

I'd advise against moving dhcp and dns off unifi unless you have a better reason to do so, because then you lose a good chunk of what unifi provides in terms of the network management. USG is surprisingly robust in that regard (unlike UDMs), and can even run a nextdns forwarding resolver locally.

DHCP is a really stupid* service for the most part. Unless you are working with multiple subnets or have some very specific settings you need to pass to your clients, it's probably not worth it to manage it yourself. I don't want to discourage you though! Assigning static IP addresses by MAC can be extremely useful and is not always an option on routers. If you want static names and dynamic addresses, that is really where you need to manage both DNS and DHCP. It really depends on how and where you want names to be resolved and what you are trying to accomplish. (*stupid as in, it's a really simple service. You want it simple because when DHCP breaks, you have other serious issues going on.)

Setting up your own DNS is worth its weight in gold. You can put it just about anywhere on your network (before your gateway, after, in China, whatever.) and your network won't even know the difference if setup correctly. You can point BIND at the root servers and bypass your ISP completely if you want. ISP DNS services suck ass, so regardless of you resolve yourself, or forward all name queries to your anon DNS server of choice you have a really decent level of control on your network. It is the service to learn if you want to keep an eye on where your network wants to talk.

Your Unifi USG must play nice with your own server, by the laws of DNS. There may be some nuances when it comes to internal protocols like WINS, but other than that, it should be just fine.

I would setup a simple VM somewhere first, to answer your actual question. It's good practice to keep core services isolated on their own, dedicated instances. This is to speed up recovery time and minimize down time. Even on your home network, DNS and DHCP are services you do not want going down. It's always a pain when they do go down.

Acronyms, initialisms, abbreviations, contractions, and other phrases which expand to something larger, that I've seen in this thread:

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