DHCP DDNS updates for secondary DNS server

Question

Hi All,

I am trying to configure DDNS updates from the ISC DHCP server to the zone that is hosted on the windows server, in the dhcpd.conf I have zone section as below

zone example.com {
primary 192.168.0.45;
secondary 192.168.0.47;
}
Where 192.168.0.45 and 192.168.0.45 are my windows DNS servers

It is working fine as expected for the primary DNS server but I have noticed that DHCP is not sending any DDNS updates to the secondary DNS server(192.168.0.47) of the zone when the primary is down for some reason, is this the expected behavior?

Getting below error
Unable to add forward map from n54c5-000001.example.com to 192.168.0.86: NOTIMP
*where 192.168.0.86 is the client IP offered by the DHCP server

I tried checking the tcpdump from my dhcp server, I can see the traffic to the secondary DNS server but the zone is not getting any update, Please guide me if need to add any setting to be configured on the windows secondary server

I came across the option "allow-update-forwarding" but this can be done in bind name servers, do we have any equivalent option also in windows DNS server

Does anyone have any idea/experience of DDNS flow when the primary DNS server is down

Thanks in Advance

Answer 1

Hi,

I came across the option "allow-update-forwarding" but this can be done in bind name servers, do we have any equivalent option also in windows DNS server

As far as I know , windows DNS server doesn't support the function of allow-update-forwarding.

In windows DNS, we always use AD integrated zones to sync DNS records. This will automatically replicate to all DCs within their replication scope settings. When one primary DNS/DC is down, other DCs can still work.

Best Regards,
Candy

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Answer 2

I am not sure if we have config setting on windows DNS servers where secondary can accept the updates when the primary is not in running mode and updates the primary when it is up

Zone transfer can provide fault tolerance by synchronizing the zone file in a primary DNS server with the zone file in a secondary DNS server. But secondary server is a read-only copy zone and not update the zone.

So I am afraid that windows DNS cannot achieve your goal.

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