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<p>The line "enable-ra" is directing dnsmasq to act as a "router
advertising daemon". The advertisement sent will include the RDNSS
default address(es). This is how IPv6 works.</p>
<p>If the <i>_client_</i> can ignore the RDNSS in the RA packet
then the DHCPv6 might have a chance of doing what you want. In
Fedora, using NetworkManager, use the option to do IPv6 "Automatic
(Address only)", then using dhcp6c, would be something to
investigate. IIRC Windows can also do "Address only" via
automatic/SLAAC configuration then use DHCPv6 for all the other
info. Android still has a ways to go to live happily in the IPv6
world, as of Android 10 - too many show stopping bugs. (keeps
dropping and reconnecting to the WiFi). If your Android version
will allow the granularity, the "Automatic (address only)" option
may help.<br>
</p>
<div class="moz-cite-prefix">On 3/25/21 3:50 AM, Hamish Moffatt
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:d263b175-2558-a2fb-eb6b-b9caec1aa7af@moffatt.email">I'm
attempting to override the DNS server for a few hosts on both IPv4
and IPv6. I've tagged the hosts and applied dhcp-option to that
tag and it's working correctly for IPv4, but I'm not having much
luck with IPv6.
<br>
<br>
I'll admit right now that I don't fully understand the use of
DHCPv6 and how DNS servers are discovered, so it might be that
this is just not possible, at least for all types of clients.
<br>
<br>
My dnsmasq is at ::1, and I want to use the DNS server at ::18 on
the same prefix. What I have is:
<br>
<br>
dhcp-option=tag:adblock,6,192.168.42.18
<br>
dhcp-option=tag:adblock,option6:dns-server,[<MY
ULA>::18],[<MY GLA>::18]
<br>
<br>
dhcp-range=set:lan,192.168.42.20,192.168.42.239,255.255.255.0,12h
<br>
ra-param=br-lan,0,7200
<br>
dhcp-range=set:lan,::1000,::ffff,constructor:br-lan,slaac,ra-names,12h
<br>
dhcp-option=lan,option6:dns-server,[::]
<br>
<br>
enable-ra
<br>
quiet-ra
<br>
<br>
<br>
What I see is that Android just has the <MY GLA>::1 address
as its DNS server. A Linux client using NetworkManager has <MY
GLA>::1 as well as the two override servers. Even when I set
<MY GLA>::18 as the server in the dhcp-option clause for the
whole network, the devices still learned the <MY GLA>::1
address.
<br>
<br>
If I remove the dhcp-option clause for the whole network then
Android shows it's using the link local address for ::1 instead.
<br>
<br>
How is Android always learning of the dnsmasq server itself as the
DNS server, and can I fix it?
<br>
<br>
<br>
<br>
Thanks
<br>
<br>
Hamish
<br>
<br>
<br>
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<br>
</blockquote>
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