FIrepower 1010 DHCP not pushing updated DNS

[EvanC75]

I am running Firepower 1010 appliance with FTD 7.4.2.  I encountered a strange issue where the DHCP server on it is not pushing the updated DNS that I set.  I setup a new DNS server so it has a different IP.  In the FIrepower 1010 device management, I went to the DNS server page and created a new group for the new DNS server.  I set it to use that new DNS group for all interfaces.  I deployed the change.  However, none of the clients are picking up the new DNS server, it is still showing the old one from the previous group when they renew the dhcp lease.  I even set a flex config to clear all dhcpd entries and set a lease time of 1 hour.  What did I miss?

Please note, this is a standalone device so I am not using Firepower management center.  I am just using the built-in web interface on the appliance.

[MHM Cisco World]

Hi 

So ftd is local dhcp server? Just confirm

Add dns to interface not meaning that ftd push dns to client you need to add dns into dhcp pool

MHM

[MHM Cisco World · Accepted solution]

https://youtu.be/exuCAz8oeZU?si=CYkoDeyd2aUu6tjn <<- this video how to change default dns server in dhcp using fdm of ftd

MHM

[MHM Cisco World]

Note:- defualt DNS push by dhcp is dns server learn from ISP' you can change this default behavior' check link I share to know how you change this default behavior

MHM

[EvanC75]

Thank you for the video.  That was definitely what I missed on going to the Configuration tab under DHCP server and setting primary DNS IP address.  I'm just getting forgetful these days.  I was able to get that switched over and now the clients are seeing it.

[Aref Alsouqi]

The DNS group you are referring to is used by the firewall itself for DNS resolutions. When you associate that group with the firewall interfaces it means that you are saying use these DNS servers for any resolution out of these interfaces, but again this is only applies to the DNS requests generated by the firewall itself, nothing behind it. However, to assign DNS servers to the DHCP clients you need to define the DNS servers in the DHCP scope as already mentioned.

[EvanC75]

Understood, thanks for the clarification.