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There is a known problem with a IPv6 Windows Client that it does not accept the DNS Server Info sent by Server via Router Advertisements, even though the IPv6 address assignment works. DNS Server information is only accepted via DHCPv6.

Now, I have dnsmasq running on my Server (which is able to allocate IPs to connected clients via Router Advertisements). However, I am not able to configure it to provide the DNS Server info via DHCP.

In the manual entry for dnsmasq I found following setting:

dhcp-option=option6:dns-server,[1234::88].

However, when I use this I see that it is still trying to send DNS Server info via Router Advertisement only, and no DHCP exchange happens. As a result Windows is not able to configure DNS Server info.

Any help would be appreciated.

  • RA cannot encapsulate DNS. But I am assuming here that you want stateless DHCPv6. So IP address is assigned by SLAAC, and then additional options can be provided by stateless DHCP, like the DNS. So you will need to configure radvd with "AdvManagedFlag off" and "AdvOtherConfigFlag on" (i.e. M-flag false, O-flag true). Then clients will look for additional options from dnsmasq. – TJJ May 17 '16 at 9:42
  • I am sorry, I just found out that DNS is deemed so important, that it was included in an RFC and is now also supported in RA sent by radvd. Look for the RDNSS option, and you won't need dnsmasq anymore. – TJJ May 17 '16 at 10:49
  • RDNSS works fine for all other clients. But Mr. Microsoft Clients (Read it as Windows Client) do not seem to accept DNS Info shared by RDNSS. It needs this info via DHCPv6 server. – Sajal May 20 '16 at 6:42
  • The RFC is from 2010. It might be that it is only working from Windows 8 onward. Are you using Windows 7 or lower? Can you try with Windows 8/8.1/10? – TJJ May 21 '16 at 22:05

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