DHCP DNS Option not as configured

Hi there, hopefully you can help me out.

I am using OpenWrt 19.07.4 r11208-ce6496d796 / LuCI openwrt-19.07 branch git-20.247.75781-0d0ab01 on a Atheros AR9344 rev 2 device.

On Interface LAN i use DHCP and configured Options for DNS like this
6,192.168.1.2,208.67.222.222,208.67.220.220
and activated strict order in advnced DNS settings.

My Client gets all 3 DNS Servers as expected, BUT also on place the IPV6 address of my router. I have no clue, where this come from. So my client never uses the correct DNS server.

I really hope you can help me out here.

You also need to configure odhcpd.
Replace IPv6 addresses with IPv4 if you have a dynamic prefix.

Thanks for your reply, but this changes nothing :frowning:

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Make sure to perform DHCP release and renew, or reboot the client.

If the issue persists, post the output:

uci show dhcp
dhcp.@dnsmasq[0]=dnsmasq
dhcp.@dnsmasq[0].domainneeded='1'
dhcp.@dnsmasq[0].localise_queries='1'
dhcp.@dnsmasq[0].rebind_protection='1'
dhcp.@dnsmasq[0].rebind_localhost='1'
dhcp.@dnsmasq[0].local='/lan/'
dhcp.@dnsmasq[0].domain='lan'
dhcp.@dnsmasq[0].expandhosts='1'
dhcp.@dnsmasq[0].authoritative='1'
dhcp.@dnsmasq[0].readethers='1'
dhcp.@dnsmasq[0].leasefile='/tmp/dhcp.leases'
dhcp.@dnsmasq[0].resolvfile='/tmp/resolv.conf.auto'
dhcp.@dnsmasq[0].localservice='1'
dhcp.@dnsmasq[0].nonwildcard='0'
dhcp.@dnsmasq[0].strictorder='1'
dhcp.lan=dhcp
dhcp.lan.interface='lan'
dhcp.lan.start='100'
dhcp.lan.limit='150'
dhcp.lan.dhcpv6='server'
dhcp.lan.ra='server'
dhcp.lan.leasetime='6h'
dhcp.lan.ra_management='1'
dhcp.lan.dhcp_option='6,192.168.1.2,208.67.222.222,208.67.220.220'
dhcp.lan.dns='192.168.1.2 '208.67.222.222' '208.67.220.220'
dhcp.wan=dhcp
dhcp.wan.interface='wan'
dhcp.wan.ignore='1'
dhcp.odhcpd=odhcpd
dhcp.odhcpd.maindhcp='0'
dhcp.odhcpd.leasefile='/tmp/hosts/odhcpd'
dhcp.odhcpd.leasetrigger='/usr/sbin/odhcpd-update'
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This line looks mangled because quotes must be in pairs.

Check the following:

cat /etc/config/dhcp

By the way, you can set up a static IPv6 lease and use the ULA address for DNSv6.

I edited this line when pasting and messed up the quote. I am using a different subnet in real. So the config is correct and there is no typo.

I guess I don't need ipv6 at home

Completely disabling IPv6 is not always possible.
But you can disable and stop the odhcpd service.

You can also intercept DNS traffic and forward it to another resolver.

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Nothing is working like it should.
I guess i am at a point to become despair

No matter what i do, DNS is still there. Even when i configure static DNS on Interface in Windows.
grafik

OpenWrt is your DHCP and DHCPv6 server, isn't it?
Did you restart the odhcpd service to apply changes?
Did you try to reboot the client?

Correct openwrt is my only DHCP server.
I just applied the settings and ipconfig /release renew
I didn't restarted the odhcpd Service it self neither restarting the client.

Should I try this?

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No change after restarting odhcpd service. DNS entry ist still present

You always need to reload/restart the service to apply the new config.
Rebooting the client makes sure it flushes all caches and requests a new lease.

If this doesn't help, then you have 3 other options mentioned above:

  • Use another IPv6 addresses to advertise DNSv6.
  • Use DNS hijacking to intercept both DNS and DNSv6 queries.
  • Disable and stop the odhcpd service.

Thanks for your help. But I guess I will just use my openwrtv router for dns queries. Not as comfortable as the other, but I guess it will do

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