Well good to know it's not just me!
I rolled back to 2.3.3.140 (along with a database backup from that release) and the issue appears to be gone. Seems like something with the latest update caused it.
I'm now seeing the normal requests from the hub and just a handful of PTR queries to local IPs over the course of an hour.
To summarize my posts:
- Significant uptick in PTR queries from the hub to my DNS server that occurred every other hour for around an hour at a time.
- DNS queries were to local IP devices attached to the hub
- Rebooting didn't work
- Rolling back to a prior release (2.3.3.140) and restoring a database backup solved the issue.
- No other changes were made to existing apps on the hub shortly prior to or at all after the update
- Appears to be similar to an older issue: Many DNS Queries from new Hub - #12 by storageanarchy
Hopefully this is something that can be looked into as I'd like to keep my hub up to date!