Windows clients not using NTP server provided via DHCP

Question

I have a network consisting mostly of Windows Vista and 7 clients and an Ubuntu server. The server provides both the DHCP and NTP services through dhcp3-server and openntpd.

In my dhcpd.conf, the subnet is declared as follows:

subnet 10.10.10.0 netmask 255.255.255.0 {
        range 10.10.10.10 10.10.10.200;
        option broadcast-address 10.10.10.255;
        option routers 10.10.10.1;
        option ntp-servers 10.10.10.1;
}

The clients don't seem to be using the NTP server though. When I capture the network traffic with Wireshark during the DHCP process, I also see no mention of the NTP option in the DHCP offer message.

I am not quite sure if the clients would have to specifically request that option to receive it or if I have to make another configuration to offer the option.

Answer 1

The registry key

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Dhcp\Parameters\Options\4

indicates that Windows doesn't actually makes use of the required option that would set the NTP server (DHCP option 42). http://support.microsoft.com/kb/121005 indicates that adding additional keys here will not have any effect.

Thus, it seems to me that it is simply not natively supported to set NTP servers via DHCP on Windows Vista/7.