[ntp:questions] Mu whole Internet crashes when server is in the pool rotation

Miroslav Lichvar mlichvar at redhat.com
Mon Apr 29 07:42:32 UTC 2019

On 2019-04-27, jeliskoski at gmail.com <jeliskoski at gmail.com> wrote:
> NTP server is working properly, I wanted to join the official pool. My
> score is 19.2 which is excellent, but my whole internet crashes !
> Even if I choose the lowest speed it is same. If I make schedule for
> deletion the server I presume is immediately remove from pool rotation
> everything is back to normal.

That sounds like your router/firewall is trying to track all the NTP
clients and exceeding the maximum number of connections.

Is connection tracking disabled for the NTP port?

With iptables it can be configured like this:

iptables -t raw -I PREROUTING -p udp -m udp --dport 123 -j CT --notrack
iptables -t raw -I OUTPUT -p udp -m udp --sport 123 -j CT --notrack

Miroslav Lichvar

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