I’ve run a chrony ntp server in the pool for about a year with no issues. The Net Speed setting has been on 10Mbits because I thought my residential cable network provider had data caps.
Turns out my ISP is unlimited (at least by their marketing department) so I tried turning up the Net Speed setting to 1000Mbits.
It seemed fine and the requests per second on port 123 ramped up, as expected.
But the normal web browser use on the Ubuntu Linux machine started becoming unresponsive, as did another nearby windows machine.
It seems the increased NTP packets interferes with DNS. Web pages are slow initially but once they start they flood in. Bandwidth is not the issue. It’s DNS.
The problem becomes so bad it starts reporting poor scores on the pool. To the point where it drops out. Bizarre?!? The machine is not overloaded. Cpu load and even network bandwidth is fine.
It’s mainly DNS. Outbound nslookups fail during these scenarios.
Ubuntu 20.04 Linux is fully updated, and mostly stock except for some standard internet hardening steps to ensure security. Chrony is configure well as a stratum 1 server using GPS time.
What’s the deal here? Why is high NTP traffic on port 123 interfering with DNS traffic?