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I have a SOHO network with a split DNS configuraiton, and I have configured my router's (a Huawei H122-373) DHCP to provide my DNS as the primary DNS.

However I have no control on the DHCPv6 of my router, which provides no IPv6 address but provides its link-local IPv6 as a primary DNS. This is an issue on some computers (only on Windows, it seems) because they first try the IPv6 DNS, thus bypassing my own.

I could manually configure each computer to use my DNS over IPv6, or perhaps disable IPv6 on each computer, but I prefer to avoid this solution.

Is there another way to do this?

Hugal31
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  • You can try to change IP preference like explained in this topic : https://superuser.com/questions/436574/ipv4-vs-ipv6-priority-in-windows-7 – S. Brottes Aug 31 '22 at 14:40
  • Thanks, but I don't see a "network-side" solution in this response. I would like to avoid modifying each computer one by one. – Hugal31 Aug 31 '22 at 14:51
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    Where is the router getting its DNS configuration from? Make sure your router is using your DNS server for all DNS queries. Make sure it doesn't know of any other DNS server addresses to use, and its DNS relay should always relay DNS lookups to your server. Also, your router might not be using DHCPv6. It might be using IPv6 Router Advertisements to get this DNS info to the clients. See if you can turn off IPv6 Router Advertisements. If you have access to the Unix layer of your router, look at preventing the router advertisement daemon (rtadvd) from running. – Spiff Sep 01 '22 at 00:51
  • I can't configure anything related to IPv6 on my router, including the DNS. – Hugal31 Sep 01 '22 at 12:36

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I found a solution, but it is far from ideal:

I disabled the DHCPv4 on my router and ran a DHCPv4/v6 server on my NAS. Now, there are two DHCPv6 server running, both with unfortunately the highest preference value (255), but since my NAS DHCP is providing a ULA address, DHCPv6 clients seems to prefer this one (as per 18.2.9. of RFC 8415).

Hugal31
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  • Can you let us more information about your configuration (share your parameters)? Do you use a Synology? I have the same problem with the box of my provider. Thank you. – Acti67 Feb 05 '23 at 19:53
  • We used a Synology NAS version 6 at the time of this problem. I manually created a DHCPv6 service on the command line which uses a custom configuration file, however it didn't survived the update to Synology version 7 and I can't remember the configuration. It was not reliable though. – Hugal31 Feb 06 '23 at 14:56