I recently expanded my home network from a /24 subnet (255.255.255.0) to a /22 subnet (255.255.252.0). This increased my available IP address range from 192.168.1.1–192.168.1.254 to 192.168.1.1–192.168.3.254, allowing me to better organize and segment devices.
Since making this change, Pi-hole is reporting a massive number of reverse DNS queries from my Home Assistant instance. It seems Home Assistant runs a periodic discovery scan and attempts to resolve hostnames via in-addr.arpa for the entire subnet.
At first, I thought this was just a harmless warning — Pi-hole logs show it blocks the offending IP (Home Assistant) for 60 seconds after the flood of requests. However, after a few days, the system becomes unstable:
CPU usage on the Pi-hole server reaches 100%.
Internet access across the network becomes unreliable or stops completely.
Pi-hole essentially crashes or stops working properly, possibly due to an overloaded log file or resource exhaustion.
So… any ideas on how to:
Limit Home Assistant’s discovery scope?
Prevent these reverse DNS floods?
Or handle the load better on Pi-hole?
Any help or pointers would be much appreciated. Thanks!
by the way, this happens with a fresh pi-hole install and a fresh homeassitan install (as HASSOS or Docker…)
I had done that with my HA setup and have noticed ZERO issues with the HA system functioning correctly. Not sure I understand why it was decided that hourly reverse DNS lookups was even a good idea. There is absolutely nothing else on my network that has that same behavior.
It is near the very top of my list of irritants about HA and the decisions made the core developer team. And the hard coded backup DNS is high on that irritant list too.
Oh it is present in /24 networks as well. That is how mine is setup. It becomes more noticeable and causes for real network wide performance issues when people are running HA in larger subnets.
Yes that is the net end change. But it can be done via GUI and the HACS addon.
Ideally I’d rather not be mucking about in that default config, but since there is no native UI way to disable the reverse DNS lookup, that is what must be done.
Presumably will lose some auto-discovery of new things added to the network. In my case though, I added some Kauf WiFi smart plugs after making that change, and they were quickly recognized by HA without issue.
I voted for and made a comment to this existing feature request to offer an ability to toggle it off without having to resort to using HACS.
