That is a great solution. I found that I can go to http://IPAddress/net/net/sntp.html and disable SNTP. I also scrambled the Primary SNTP Server Address, and put the synchronization interval to as high as it would go; 100 hours.
SNMP is completely different than SNTP. SNTP is basically just a minimal NTP client that just queries the time and doesn't attempt to do anything like compensate for network latency or use multiple NTP servers.
This is the real solution. Pretty much all printers accept read/write from public by default and share a lot of info about themselves. Any program on your computer could do this if it wants, the only surprise here is that it took this long for anyone to bother.
That should be the solution for everything but unfortunately I'm dealing with containers that advertise their IP via Bonjour (or whatever the new thing is). But since they run in a container they get their 172.19.0.0/24 IP, so they broadcast the wrong one.
Then there is the issue of certain devices only accepting things like HomeKit via a barcode and/or discovery, and not via IP addresses.
If I could just do IP addresses it would be so much more easy to cordon off things. IPs can talk across networks with ease, no hacks required, but at least I control it.
Inside of a network it's very hard to selectively allow / deny traffic.
https://help.brother-usa.com/app/answers/detail/a_id/164663/...