21.7.2_1: DHCPv4 - do not send out NTP-servers (option 42)

[Udo]

Hello,

I've configured "Services -> DHCPv4 -> [Interface] -> NTP servers" with one IP.

A packet analysis with Wireshark shows that OPNsense DHCPv4 do not send out this NTP-server, option 42 is missing in DHCP-packet. Why is that?

Udo

[MartB]

I can confirm, i dont see any option 42 being set in the offer.
I dont know if it ever worked tho!

Code Select Expand

grep "ntp" /var/dhcpd/etc/dhcpd.conf
  option ntp-servers 10.0.1.1;


[larsd]

is your client requesting option 42?

[franco]

That's a good question. :)


Cheers,
Franco

[MartB]

The option is not directly requested, but i wonder where the behavior difference to the new version of iscs dhcp implementation (https://www.isc.org/kea/) comes from.
Kea sends it to me all the time regardless of the discovery and it gets ACKed by the client at the end.

[Fright]

@MartB
based on https://kea.readthedocs.io/en/latest/arm/dhcp4-srv.html#id2
by default Kea should also not send this option if it is not requested (perhaps the 'always-send' flag was used?)

[Patrick M. Hausen]

TIL something new - thanks guys. I always thought DHCP would just send all configured options to everybody asking on a subnet and it was up to the client to decide which ones were relevant and which ones were not.
So this is a request-response protocol ... interesting. Need to read up a bit on DHCP.

Kind regards,
Patrick

[MartB]

@MartB
based on https://kea.readthedocs.io/en/latest/arm/dhcp4-srv.html#id2
by default Kea should also not send this option if it is not requested (perhaps the 'always-send' flag was used?)

Checking back with a colleague that has kea running, trying to get a pcap so i can check whats actually going on there. This was just a quick test for us bcs we were both running win10.