Propagate local time over NTP to LAN

I have synchronized my L3 switch to an external time server, this is working correctly. However I'm in Europe and we have CET/CEST switching and I get UTC from the configured time server. I did setup the timezone and the summer-time in my switch (shows the correct time when I use "show clock"), but my switch propagates the NTP (UTC) time towards my LAN. (I know this is the normal operation)

My question is, can I propagate with NTP the local (CET/CEST) time towards my LAN clients, or are there any other method to do this? The problem I have that I can't setup CET/CEST switching on my clients, they do not support this. (I have PLCs in my LANs, and they're only capable of GMT settings)

Are there any solution for this, or I must use a separate time source?

Thank you very much!

can I propagate with NTP the local (CET/CEST) time towards my LAN clients, or are there any other method to do this?

No, not with NTP. NTP has no concept of local time at all, its all UTC. All the packet contains is a few time stamps with seconds and fractions of a second from an epoch.

Do not attempt to configure "wrong" offset NTP servers to do local time zone offsets. I have never seen this work, it makes good robust NTP configurations difficult.

General purpose computers have (and keep updated) a tz database such that they can be configured with say Europe/Berlin and have correct local time even when the rules change.

A rugged, embedded, or otherwise dumb computer may not have a tzdata package, or a means to update it, or reasonable time and date software. Almost certainly your PLC is lacking some of these. That KB article on how to sync time to controllers is missing details on what format or time zone everything is in, which doesn't raise my confidence that internally is a reasonable UTC clock with time zone offsets.

Unfortunately your options may be limited to exporting data to a system with a full featured clock, leaving it on UTC forever, or cursing daylight savings time every year when fixing offsets.

Of course you can propagate whatever time zone's time through NTP, you just need to make sure

• there will be only 1 time source on your LAN to mitigate the danger that your clients will receive conflicting timestamp messages and switch back and forth
• your time source will broadcast the time in the time zone you intend to

In other words: If the time source in your LAN is the L3 switch, this would be the device which either has a setting to "traslate" the time zone for NTP clients or not. In case your L3 switch isn't capable of that, you will need a different time source which is.