DNS server configuration under ipv6-dhcp is not working

[Eisai]

I have my own DNS server located at 192.168.1.200, I want to use that one as the only one, also I want to use ipv6 as well.

Here is DNS config under client, it is assigned by DHCP server running on my RT-AX88U (Merlin firmware of course).
DNS Servers . . . . . . . . . . . : 2600:6c50:607f:f3f0::1
192.168.1.200

2600:6c50:607f:f3f0::1 is ipv6 address of my router, I just can not take this DNS address out of DHCP server, already tried many ways to config DHCP server on my router including SSH.

turn out, I must use my router as first DNS server, or disable ipv6 capability to use my own DNS server only.
Right now I'm using 192.168.1.200 as WAN port DNS server on my router, It is works, however it is a little bit wired.

Any idea how to fix that?
Thanks a lot!

 

[Eisai]

I believe Asus router is running a DHCP6 server to assign ipv6 address instead Dnsmasq, that's why those part in picture below are not working. however I don't know how to config DHCP6 server on router.

 

[Tekneek]

My solution to this problem was to create a file named dnsmasq.postconf in /jffs/scripts with the following contents:

#!/bin/sh
CONFIG=$1
source /usr/sbin/helper.sh

pc_replace "dhcp-option=lan,option6:23,[::]" "dhcp-option=lan,option6:23,[ipv6 address of DNS server]" $CONFIG

Upon restart, it pushes the desired IPv6 DNS address to all clients.

 

[Eisai]

My solution to this problem was to create a file named dnsmasq.postconf in /jffs/scripts with the following contents:

#!/bin/sh
CONFIG=$1
source /usr/sbin/helper.sh

pc_replace "dhcp-option=lan,option6:23,[::]" "dhcp-option=lan,option6:23,[ipv6 address of DNS server]" $CONFIG

Upon restart, it pushes the desired IPv6 DNS address to all clients.

I can't believe it's works!
I already spent 20 hrs work on it, You just saved my life!

 

[rgnldo]

With the FW Merlin 384.13 everything is working fine, set up nothing.

 

[Tekneek]

With the FW Merlin 384.13 everything is working fine, set up nothing.

That is the router's IPv6 address, which is exactly how it has worked for years. We were talking about having a different DNS server assigned.

 

[ColinTaylor]

But for some reason, my clients are still not getting my ipv6 DNS address.

Do a "cat /etc/dnsmasq.conf". The format of the line you're trying to replace may have changed in subsequent firmware versions.

 

[SomeWhereOverTheRainBow]

another solution that worked for me in the past was to reference a link local address for listening on my DNS server like fe80:: as a link local option; in doing so, i did not have to manipulate any of the routers setup as far as ipv6 goes.