DNS for LAN clients

[rampitec]

I'm a little confused. Router is configured:

WAN: DNS1 = 8.8.8.8, DNS2 = 64.6.64.6, Connect to DNS Server automatically = no
LAN/DHCP: Advertise router's IP in addition to user-specified DNS = yes, DNS1 = empty, DNS2 = empty

I would assume a DHCP client should only get router's address 192.168.1.1. There are no specific settings on the client. Client has:

DNS1 = 192.168.1.1, DNS2 = 64.6.64.6

Why DNS2 is set on the client? Even if set, why is it set to DNS2 of WAN?!

 

[ColinTaylor]

You are correct, that shouldn't be happening. It's either a bug or a misconfiguration somewhere.

Have you confirmed that it applies to all of your DHCP clients and not just one?

What firmware version are you running.

 

[rampitec]

FW is 380.65_2 from Merlin.
It looks like it only happens on one client. The client is Panasonic SIP phone, so I cannot telnet to it and see in details... Maybe it remembered info from oldrr times, but then it shall survive phone reboots.

 

[rampitec]

Weird. Panasonic indeed caches old DNS settings, I have just verified it. Not a router issue.

 

[ColinTaylor]

Thanks for letting us know.

 

[rampitec]

BTW, if it comes to DNS. A very nice feature would be to be able to specify what to send as a DNS for an individual client in the DHCP config.

That is because on modern Android there is no way of changing it.

 

[ColinTaylor]

You can use Parental control > DNS Filtering to force a specific client to go to a specific DNS server (but that client looses the ability resolve local hostnames).

Alternatively, you can always customise dnsmasq any way you want through the use of a custom config file.

 

[rampitec]

Ugh... Android is extremely unfriendly OS. I managed to assign it what I want:

dhcp-range=mobile,192.168.1.16,192.168.1.31,255.255.255.0,86400s
dhcp-host=XX:XX:XX:XX:XX,android-device,net:mobile,192.168.1.16,infinite
dhcp-option=net:mobile,6,8.8.8.8,64.6.64.6
dhcp-option=net:mobile,23,[2001:4860:4860::8888],[2620:74:1b::1:1]

It gets desired DNS and after a second resets property net.dns1 to ipv6 of the router

 

[ColinTaylor]

Just a guess ('cos I'm not using IPv6), but perhaps dnsmasq is in conflict with another process that is doing IPv6 Router Advertisements.

 

[rampitec]

Well, the advertisement cannot be disabled, ipv6 will not work then. I would just disable ipv6 altogether, but Android then invents its own ipv6 address and tries to work through a tunnel, which also does not work.

 

[rampitec]

Now that works So the problem was that stateless ipv6 took the whole range and my client was served by that main range. So I changed IPV6 to stateful, which allows to assign address diapason.
Then this:

dhcp-range=mobile,192.168.1.16,static,255.255.255.0,86400s
dhcp-range=mobile,::500,::999,constructor:br0,ra-only
dhcp-host=XX:XX:XX:XX:XX:XX,android-device,net:mobile,192.168.1.16,infinite
dhcp-option=net:mobile,6,8.8.8.8,64.6.64.6
dhcp-option=net:mobile,option6:23,[2001:4860:4860::8888],[2620:74:1b::1:1]

In addition that allows to name an android host, which is usually impossible.
Thank you for the idea!