NTP Server CCTV Network

Good afternoon,
Our problem consists of an installation with 7 Exacq servers and about 100 IP and analogue cameras. Our client has no NTP server, nor internet connection.
The cameras are synchronized each one with its own Exacq, but I have no way to synchronize all the exacq between them.
When we have an alarm on the alarm monitor, the live video usually has a delay of several seconds because it doesn’t have NTP.
We have tried to synchronise all with one Exacq, all the cameras and recorders, it works, but after 15 days we have big delays again.
We have to restart the Exacq services to synchronise again and this is not a solution.
Any idea what we can do?

Thanks,
Patricia

Without adding hardware, the best option would be to have all of the Servers sync with one source (pick one Server to act as your time source). Then have that Server sync to itself (127.0.0.1).
NOTE: You will still deal with time drift, but at least they will drift generally together.

Some customers with very restricted networks opt to get a GPS based NTP Server which plugs in to your network as an IP device. Then all devices will be synced to a reliable source. These are not an Exacq product, but have worked successfully for other customers.