@eeiciap 

My issue is that I have an internal DNS that I need on the WAN because I use VPN. I need VPN clients to be able to query internal DNS so clients can resolve other clients and internal servers by hostname.

I want my topology to look as follows:

I'd crunch this router with DDWRT, but I wanted to give TP-Link the benefit of the doubt first.

Having the same issue. Every time I try to use PiHole as a local DNS server, within a few days my entire network changes IP addresses and screws up all my static-set-IP devices like my raspberry pis, NAS, Plex and personal web server.

If TP-link can't even give us the professional courtesy of an estimated time for patch, then I will definitely be switching network gear this year.

@flashVenom 

I have simmilar issue on my siede. If I set WAN DNS to local IP all ip configs go to shi..... when can we expect fix for this?

@flashVenom Yeah .. I still haven't gotten a response. I know how to make the software change to fix his DNS issue, but my model is locked down from SSH where I can modify the CLI. I tried DDWRT, but the firmware didn't stick because the model hasn't been verified by DDWRT team (thought I should test it anyway).

Sorry you're having similar issues with TP-Link products.

Is this issue resolved. I just purchased TPLink Archer C6 and seeing same issue. On reboot the router IP changes. This causes no Internet access on the connected devices.

Please help, in case anyone has a resolution to this ! 

@TP-Link  can we get an update? Was this users problems solved? There are obviously lots of us having this same problem. I was hoping TP-link would either publish "a fix" or update the firmware - which, if firmware patching this issue, I'm hoping you'll *let us know the bug has been fixed in the version history.*

Every time I set a static IP for DNS it resets my whole network IP mask and all my devices go berserk

@eeiciap 

I was able to resolve this by using both my Windows Server 2016 DNS server as a primary and the Synology NAS DNS server as a secondary DNS. The configurations allow both to be a master zone, but the Synology DNS server gets updates from the Windows Server 2016 DNS server. 

Create a master zone and make sure the Zone ID and Domain Name are identical to your Windows Server 2016 (or other) DNS server. After creation, right click the master zone and edit the SOA (State of Authority) record. This should be the FQDN of your primary DNS zone (ie. dc-server.domain.local). Email cab be anything (ie. hostmaster.domain.local). You'll need to put in any static DNS entries, devices that have static IPs assigned (ie. nas.domain.local -> 192.168.50.20).

This might be a bit much for the next step, but I killed all DNS records established through DHCP and I killed all dynamic DHCP records so that new records established on the primary DNS server were copied over to the secondary. It seemed to not work for me when I tried renewing a device's network interface.

Once the records were all established, I went into the network interface of the NAS to put in the secondary DNS server (this is my Synology NAS DNS) on the LAN 1 interface. For watever reason, The Synology NAS can't query my Windows DNS Server and from the articles I've read here, this just isn't working for some reason. What it can do is query its own DNS server which is now getting updated from the primary DNS server.

Also of note, my domain controller is not only my DNS server, it is also and active directory. Before establishing any other services on my NAS, I linked it to my domain so it is joined to the domain and set as an authorized device to update DNS records. My assumption is anyone on this thread is in the same situation so if you're attempting in some other manner, your mileage may greatly vary.

Once everything was properly configured, I could query DNS records by hostname and resolved the appropriate device IP over the VPN connection.

I really do hope I'm not leaving anything out as it took me forever to get this working. Please feel free to add any steps you may have taken (or left out) and got this working.

Bottomline: You need to use the Synology NAS as a secondary DNS and set on your LAN to resolve hostnames to IPs over VPN.

And apparently this has nothing to do with the original post, but I hope it helps someone.

@TP-Link 

IP conflict for the DNS on WAN or LAN or both? Or a conflict on some other IP on the network? Do I need two seperate DNS ips?