Disable announcing NTP server in DHCP

RouterOS General
1

A friend is currently trying to prevent NTP servers being announced to DHCP clients. The NTP sever is disabled, and no NTP server is set in the DHCP network section, but clients are still receiving NTP servers via DHCP (Its using those setup in the NTP client section)

Any ideas? Thanks.

[matthew@HQ] /system ntp server> print
              enabled: no
            broadcast: no
            multicast: no
             manycast: no
  broadcast-addresses:

The client element is active-

[matthew@HQ] /system ntp client> print
          enabled: yes
             mode: unicast
      primary-ntp: 139.143.5.30
    secondary-ntp: 139.143.5.31
  dynamic-servers:
  
  [matthew@HQ] /ip dhcp-server network> print detail

 1 ;;; Main LAN
   address=10.10.10.0/24 gateway=10.10.10.254 dns-server=10.10.10.254,8.8.4.4 wins-server="" ntp-server="" caps-manager="" dhcp-option=""
A question regarding DHCP-server and NTP option
2

Same for me, DHCP server is announcing the NTP server from its SNTP client configuration, althought it’s not configured to provide NTP server to it’s DHCP clients. Is there a way to disable the announcement of NTP server to the DHCP clients somehow?

3

What does /ip dhcp-server network export show?

4

This is like the DNS bug again, but in NTP.
You’d have thought they’d check both when fixing one, but it seems not.

5

This behavior still seems to be on v6.45.9 (long-term).

It would be nice to configure this behavior - as I do not believe it’s possible to do it if you do configure it by hand.

Having said that - having no NTP servers set in the DHCP scope should not be sending NTP servers to DHCP requests.

6

Still true in 6.49.3.

The ntp servers are being offered via DHCP options, even though no DHCP options are configured. I really want to be able to enable this on a per-network basis.

7

Issue is still persist in v7.1.1

8

This is interesting!
I just came across this very same issue in v7.14.2.

I’d say this needs to be made configurable: if enabled, DHCP Server should either announce NTP address(es) used by the NTPClient or address(es) configured under ‘/ip/dhcp-server/network/’.
But if ‘NTP Servers’ option is NOT enabled in ‘/ip/dhcp-server/network/’ - obviously, no NTP address should be announced.

Is there a reason why it’s not made to work like this? (for about 10 years already)

9

I added the following DHCP option then created an option set and added it to my DHCP server:
/ip dhcp-server option add code=42 name=42_NTP_empty value=“”
/ip dhcp-server option sets add name=servers options=42_NTP_empty
/ip dhcp-server set 0 dhcp-option-set=servers

This does not disable NTP announcing actually but announces an empty string. This made my Debian 12 distribution to use its preconfigured NTP servers.

Note: please do not apply the 3rd command line directly to your system. Modify it according to your needs or use Winbox as an easy and spectacular way to edit your existing DHCP server.

You can learn more here:
https://help.mikrotik.com/docs/spaces/ROS/pages/24805500/DHCP#DHCP-DHCPServer
https://www.iana.org/assignments/bootp-dhcp-parameters/bootp-dhcp-parameters.xhtml