dns setting for client

Simon Hobson dhcp1 at thehobsons.co.uk
Fri Oct 4 12:29:48 UTC 2019

Julie Xu <J.Xu at westernsydney.edu.au> wrote:

>We have changed DNS server, and on dhcpd.conf I did change the dns to
>new server, but, on the client site, if you do ipconfig/all, you can
>see the dns is still pointed older dns server, if there is possible to
>on dhcpd.conf to force dns server change?

As soon as you have updated the server, it will start serving the new information. However, it's a pull transfer and relies on the client to ask for it. By the end of your max-lease-time setting, you can guarantee that there are no active leases that we're given with the old settings.

However, I vaguely recall some discussion in the past related to clients that didn't update settings when renewing an active lease. I don't know whether your clients fall into that group.

As already said, manually releasing and then renewing the lease at the client end should do it. Or just wait...

A brute force method would be to change your IP range and force clients to get a new lease. Add a new range, set the old one to "deny booting", and then tne server will Nack any renewal requests for the old addresses.  This will break all existing connections.

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