How to synchronize time in CentOS7 with one way traffic?

Question

CentOS

A non-trivial task has appeared: it is
necessary to synchronize the time on several servers running CentOS 7 that do not have an active connection. Each server has an ethernet port, which receives mirrored traffic from the switch for analysis. That is, the traffic goes only in one direction "to the server".
They voiced the idea: once every N hours, the NTP server sends a packet to broadcast or to some specified address, the servers catch and synchronize the time.
Is it feasible?

Answer 1

It is better to attach a GPS receiver or a PPM signal receiver than to invent NTP