topic Re: Android DNS - doesn't use nameserver on LAN? in Tech Help - Software/Hardware etc

Android DNS - doesn't use nameserver on LAN?

7up — Tue, 05 Dec 2017 18:43:22 GMT

Hi all,

I've got my DHCP server working in order to hand out the IP of my nameserver which hosts several domains internally on our network. This works fine on windows machines, they do as they're told and use my nameserver and everything is ticketyboo.

On our android devices name resolution drops dead. On the GUI for my nameserver I can see that a request comes in, and that one is issued, wireshark confirms it was replied to and that the packet conforms but android keeps saying that it cannot resolve the domain.

When i set the nameserver ip back to the router (or an external IP) all is good again. It seems that it is only a lan problem where android deliberately refuses to act on information being returned from a nameserver that is on a different IP to the router / gateway. I've even tried the spare wifi AP in case it was getting upset about the nameserver being a hop further away than the router but it still didn't like it.

So my question.. is this a known android thing? - I've found a few references to it online but all the symptoms seem to vary slightly (though pi-hole users have been complaining). I'm just wondering if there is any sort of workaround other than using an external nameserver with internal A records which isn't ideal..

Re: Android DNS - doesn't use nameserver on LAN?

HairyMcbiker — Tue, 05 Dec 2017 18:49:22 GMT

Yep seen this on mine. I think there is a dns changer on the play store, but it may require root access, but not tried it I just use ip addresses.

Re: Android DNS - doesn't use nameserver on LAN?

Anonymous — Tue, 05 Dec 2017 18:52:15 GMT

Could you set the router's DNS to point at your internal nameserver.

Therefore your Android will request from router, that will in turn ask your nameserver, which will get it's info from your WAN bypassing the router.

If your nameserver is caching, then that will still be faster than Android using the router alone.

It may or may not work with your router, but it would work with mine.

Re: Android DNS - doesn't use nameserver on LAN?

7up — Tue, 05 Dec 2017 19:25:44 GMT

We use the hub one which means i can't do that - plusnet lock the thing so you can't change dns.

Re: Android DNS - doesn't use nameserver on LAN?

MJN — Thu, 07 Dec 2017 20:37:00 GMT

Just to be clear, if you manually configure your Android device to use your local nameserver (not the router) for DNS resolution then that also doesn't work? Or is it only when forcing the configuration via DHCP that you are having problems?

Re: Android DNS - doesn't use nameserver on LAN?

HairyMcbiker — Fri, 08 Dec 2017 10:01:24 GMT

You could disable the dhcp server on the Hub 1 and use the pi-hole to do both. That MAY fix it.

Re: Android DNS - doesn't use nameserver on LAN?

MJN — Fri, 08 Dec 2017 10:06:36 GMT

I had assumed that's how it was configured, otherwise having two DHCP servers on the LAN is going to cause issues.

Re: Android DNS - doesn't use nameserver on LAN?

HairyMcbiker — Fri, 08 Dec 2017 10:09:55 GMT

Just used DNS Changer (non root) from the play store. Changing to my pi-hole server dns let me use http://pi.hole as an address (you have to use http://or google grabs the query) if you don't want to use pi.hole as a dhcp server.

Re: Android DNS - doesn't use nameserver on LAN?

7up — Fri, 08 Dec 2017 21:37:45 GMT

@MJN wrote:

Just to be clear, if you manually configure your Android device to use your local nameserver (not the router) for DNS resolution then that also doesn't work? Or is it only when forcing the configuration via DHCP that you are having problems?

Manual configuration never worked either.

Yes hubone DHCP was turned off during trials.

Will give pi-hole trial a go at some point, be interesting to see if android can see it!

EDIT: Guys you're confusing me lol. Android can see the nameservers, it's just refusing to act on the returned results for whatever reason as i previously stated. I'm going to try the app HMcB has recommended and see if that makes any difference but i have a hunch this is an android glitch or security 'feature'.

Re: Android DNS - doesn't use nameserver on LAN?

7up — Sun, 17 Dec 2017 03:35:44 GMT

Ok I've got this fixed!!!

My dns server wasn't setting the RClass in the returned resource records. I've updated that and now it sets the results to 1 for IN and everything works on android devices as it should. Android DOES use local nameservers it's just a bit pickier than windows which apparently doesn't worry about the RClass.

Good old wireshark..

Sorry that doesn't help you @HairyMcbiker, no idea whats up with pi-hole

Re: Android DNS - doesn't use nameserver on LAN?

MJN — Sun, 17 Dec 2017 10:23:22 GMT

Is this DNS server one you've written yourself? If so you really ought to have made that clear from the outset!

Re: Android DNS - doesn't use nameserver on LAN?

Anonymous — Sun, 17 Dec 2017 11:04:12 GMT

I had always assumed that this topic was about a self written DNS / DHCP project

Re: Android DNS - doesn't use nameserver on LAN?

MJN — Sun, 17 Dec 2017 11:07:20 GMT

There's nothing suggesting that in the thread.

Re: Android DNS - doesn't use nameserver on LAN?

Anonymous — Sun, 17 Dec 2017 11:19:53 GMT

That may be so, but this is @7up , and he does have a history of doing such things - which is fine !

Re: Android DNS - doesn't use nameserver on LAN?

MJN — Sun, 17 Dec 2017 11:23:23 GMT

Ah, okay, I'll bear that in mind in future! 😉

Re: Android DNS - doesn't use nameserver on LAN?

7up — Sun, 17 Dec 2017 11:27:08 GMT

@MJN wrote:
Is this DNS server one you've written yourself? If so you really ought to have made that clear from the outset!

Yes. Both are custom written. Sorry I thought I'd made that clear but reading the op again I can see where the confusion could arise. Most here know I've been working on this for a while hence I didn't think about clarifying that as clearly as I should have.

Anyway iis working now! I had given up but tried a 14 day trial of simple DNS and noticed that android did take notice of DNS replies so armed with that new found knowledge I realised it can be done, I just needed to dig further.

Re: Android DNS - doesn't use nameserver on LAN?

MJN — Sun, 17 Dec 2017 11:41:26 GMT

No worries; I only pop in from time to time so don't have my finger on the pulse of who gets up to what!

Re: Android DNS - doesn't use nameserver on LAN?

Anonymous — Sun, 17 Dec 2017 15:29:46 GMT

Writting your own DHCP Server and your own DNS Server, with its own GUI, someone has way to much free time on their hands

Re: Android DNS - doesn't use nameserver on LAN?

7up — Sun, 17 Dec 2017 19:51:14 GMT

There aren't many free windows offerings for either server so I figured I might as well come up with my own. At least that way I can add extra functionality that I may need in the future. Plus it was a good exercise in dealing with bits and bytes in their raw format along with data packets etc.

Now I just need to make both programs available for free online and gain a user base to help me towards a better future..

Re: Android DNS - doesn't use nameserver on LAN?

MJN — Sun, 17 Dec 2017 20:02:49 GMT

What about BIND? It is practically ubiquitous and with nearly 30 years of history rather well developed!