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DNS local service only not working

0 votes
1,056 views 4 comments
by anonymous

RUTX11, firmware RUTX_R_00.07.01.2

We wish to you use Custom DNS ServErs only for client.

"Local Service Only" is selected but it forwards queries to ISP.

Seems to behave intermittently, sometimes it works, sometimes not.

Seems to be a bug?   Anyway to force it?  We could probably put the custom DNS servers on all the WAN interfaces, but it shouldnt it work automatically when 'local Service only' is selected?

Thanks in advance..

1 Answer

0 votes
by anonymous

Hello,

Have you specified some specific listen/excluded interfaces at Network>DNS in the WebUI? By default, if no interface is specified, the router will still listen for DHCP and DNS requests on all interfaces, even if the "local service only" option is enabled. The option itself specifies that the router will accept DNS queries only from hosts whose address is on a local subnet, i.e. a subnet for which an interface exists on the server.

Best regards,

Tomas.

by anonymous
Hi Tomas,

Thanks for your reply.  No I had not specified list/exclude interfaces.  But I have tried it just now selecting to exclude the WAN and Mobile interfaces but still not working correctly. Also set the dns cache to zero in case.  It is made more difficult to troubleshoot as the 'log dns queries' option is not working correctly on some devices. On this device I have 'not enough space left' in system log, but it is a pretty standard setup with only 1 package installed (Zerotier).

On older firmware there was an option on WAN interface to exclude ISP advertised DNS but is not available in this firmware version.

Any other suggestions as this is creating quite a problem for us as we need DNS requests from Clients to go to specified DNS Filtering servers only..

On all interfaces we have not set DNS Servers as we want the Teltonika to act as the DNS proxy and we have specified our custom DNS servers in the network->DNS section only.  We want all user interfaces to have queries forwarded to our custom DNS servers only.

I have also tried setting the listen interface to LAN only but device still resolves via ISP DNS advertised servers.

Can you advise further?

Thanks in advance.
by anonymous

Thank you for clarifying. If I understood you correctly you'd like to set custom DNS servers on WAN/mobile interfaces. In that case please login to the router via WebUI and navigate to Network > Interfaces then edit whichever WAN interface you'd like to change (WAN/MOB1S1A1). Once the configuration window with general settings opens up, on the side bar, click on "Advanced Settings" and fill in the field "Use custom DNS servers". Make sure to save & apply the changes. This should force the changed interface to use only specified DNS servers. For visual representation, this setting can be found on our wiki page by using the manual. I'll leave a link to it down below:

https://wiki.teltonika-networks.com/view/RUTX11_Interfaces#Advanced_Settings:_DHCP - for physical WAN port

https://wiki.teltonika-networks.com/view/RUTX11_Interfaces#Advanced_Settings:_Mobile - for mobile interfaces

Best regards,

Tomas.

by anonymous
Hi Tomas.

Well what we want is that DNS queries for clients only use the custom DNS servers we specify....

So we can go and modify every single wan interface and mobile interface, but that is a lot of work to complete for all devices we have ..also am a bit worried about changing a mobile interface dns in case the ISP requires their own for some reason.  In earlier firmware the 'use dns servers advertised by peer' was much more effective. But this option is no longer in the current firmware. I don't understand why some of these settings keep changing with every firmware version...  It means we have to go back, validate everything, and often make changes then across the entire estate...  Just some feedback, but thanks for your help.
by anonymous

The only different part in this case is the front end and due to absolutely brand new WebUI some settings may be in different places. In this case the required setting works in the exact same way under the hood of RutOS, the only difference now is that if the field "Use custom DNS servers" is left empty, the device will use DNS servers provided via DHCP from another peer. If it's filled in then the router ignores DNS servers which would normally be acquired via DHCP and instead uses specified DNS servers.

Regarding the changes - yes, some of the settings may be in different place when comparing RutOS with legacy firmware (or completely missing if some feature was deprecated) but there's a reason behind every change. Also, we generally advise to test out latest (or simply speaking newer) firmware before upgrading every device in production.

Best regards,

Tomas.