when using IPV6 DNS, RouterOS using 2620:0:ccc::2 as dns server instead of my own dns server

RouterOS General
1

my env is RB450Gx4. routeros 6.46.7 longterm
when I use IPV6 DNS to resolve the domains . I found that it using the 2620:0:ccc::2 server instead of the server I set manualed like “2001:4860:4860::8888” or others.
whatever I set myself, It just use the 2620:0:ccc::2 server to query the domain’s dns record. but I can’t access the 2620:0:ccc::2 server, so I can’t resolve the domain’s dns record when I using IPV6 only.
I found these from the torch tools. when I use nslook utils to resolve a domain, like www.google.com or other else. In the torch windows, I can fand that , from my pc’s ipv6 address connection to 2620:0:ccc::2:53, and there were not connection to my own dns servers address. But I don’t set the 2620:0:ccc::2 dns server. and I can’t find the config in my routeros configs.

So, How to remove this setting? I just wanto use my dns servers.
and why routeros redirect my dns request to 2620:0:ccc::2 server?

2

According to whois info, the address belongs to OpenDNS.

On router you want to check “/ip dns print” and it could be either in “servers” or “dynamic-servers”. Other possible location would be options in DHCPv6 server, you’d see it in “/ipv6 dhcp-server export”.

If it’s not there, it could be something on PC, it didn’t have to get it from router. It could be configured manually, or perhaps some program may be setting it, anything is possible.

3

I clearlly confirmed “/ip dns print” and “/ipv6 dhcp-server export” result not contained the address "2620:0:ccc::2 . and my PC don’t have set it too. because if I dail up with my pc directlly the nslookup command can return result with my own dns server. and my cell phone also has the problem. if I connect the wifi (AP connect to RouterOS) I can’t resolve domain with my ipv6 dns server and if I use the cell phone data it can resolve domian with my ipv6 dns server . the both dns server is same cause I used dig or nslookup command to use the same ipv6 dns server.
I don’t know why it use 2620:0:ccc::2 as the default dns server whatever I set.

4

It must come from somewhere, but RouterOS doesn’t have any hardcoded DNS servers. In your first post you wrote that you see connections to this server from your PC’s address. So if the PC is sending those packets, you need to look there. If it would be true that it got the server from router, you’d see it in PC’s config (e.g. “ipconfig /all” in Windows). If you don’t, then you can use packet sniffer on PC, to verify that it’s really what the PC is sending. You can also use it to capture initial communication with router, when you connect it to network, and you’d see the server’s address in RA or DHCPv6 messages, if it’s really coming from router. But then it would be real mystery, if router’s config doesn’t contain it.

5

I found the murderer! IT’S NETGEAR R7000!
when the R7000 is set to AP mode, It will occur the problem.
when the R7000 is set to Router mode, the problem is gone…
But I think the AP mode should do nothing but only offer wifi aceess ablilty, why it hijack the ipv6 dns server to 2620:0:ccc::2 …
It don’t use RA or DHCPv6 protocal to send ipv6 dns setting to client, it just redirect the dns request to server 2620:0:ccc::2 instead of my own ipv6 dns servers…confusing..