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Author Topic: DNS relay stops working.  (Read 257 times)

ericy

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DNS relay stops working.
« on: November 21, 2018, 04:58:58 AM »


I have a DIR-842, HW version C1, FW version 3.10.  I have had the thing up and running for over a month now without any problems, but just yesterday I had problems where none of the clients could access the internet.

The problem was that the DIR-842 tells clients to use it for DNS when the client uses DHCP to get an address, but for some reason the DNS stopped working.  Thus all of the clients could no longer connect with anything.   I could use nslookup to query the ISP DNS server directly, and that was working correctly.

d:\temp>nslookup
DNS request timed out.
    timeout was 2 seconds.
Default Server:  UnKnown
Address:  192.168.0.1

> www.google.com
Server:  UnKnown
Address:  192.168.0.1

DNS request timed out.
    timeout was 2 seconds.
> server 75.75.75.75
DNS request timed out.
    timeout was 2 seconds.
Default Server:  [75.75.75.75]
Address:  75.75.75.75

> www.google.com
Server:  [75.75.75.75]
Address:  75.75.75.75

Non-authoritative answer:
Name:    www.google.com
Addresses:  2607:f8b0:400c:c06::68
          74.125.141.103
          74.125.141.104
          74.125.141.99
          74.125.141.147
          74.125.141.105
          74.125.141.106

> exit

Turning the DNS relay off and on in the DIR-842 corrected the issue - for now, anyways.  But I am tempted to change the router to leave this off and hardcode the ISP DNS servers just to prevent a recurrence.

Any thoughts?  I don't see any kind of error logging that this thing does - unless you enable a syslog server, and it isn't clear what kind of information one gets if one enables that.
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FurryNutz

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Re: DNS relay stops working.
« Reply #1 on: November 21, 2018, 08:41:37 AM »

Link>Welcome!

  • What region are you located?

DNS Relay should work enabled. I always keep mine disabled unless I'm doing any router management stuff that required DNS Relay. You can configure any DNS for the router to use. ISP or custom. I use cloudfare and quad9.

Internet Service Provider and Modem Configurations
  • What ISP Service do you have? Cable or DSL?
  • What ISP Modem Mfr. and model # do you have?
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ericy

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Re: DNS relay stops working.
« Reply #2 on: November 21, 2018, 10:11:40 AM »

Link>Welcome!

  • What region are you located?

DNS Relay should work enabled. I always keep mine disabled unless I'm doing any router management stuff that required DNS Relay. You can configure any DNS for the router to use. ISP or custom. I use cloudfare and quad9.

Internet Service Provider and Modem Configurations
  • What ISP Service do you have? Cable or DSL?
  • What ISP Modem Mfr. and model # do you have?

We are in North America - ISP is Comcast over cable.   Cable modem is ARRIS Surfboard SB6183.

It did work enabled for over a month, and then it stopped.  We weren't even in the house when it happened, so it wouldn't have been anything we were doing directly, but there are devices such as TiVo and a pair of Trane thermostats that are always connected even if we aren't here.

There seems to be very little in the way of diagnostics that one can use on this model - syslog is about it.  No SNMP, and nothing in the web interface.  Turning off the DNS relay probably means that anything that already has a lease will stop working.
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FurryNutz

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Re: DNS relay stops working.
« Reply #3 on: November 21, 2018, 10:17:16 AM »

No, disabling DNS relay only means that the router will not be the proxy for DNS between the internet and your devices. So if you disable DNS relay, it means that your devices will get DNS either from your ISP or if you input custom DNS, this will appear on your devices.

Has a factory reset been performed to see if DNS Relay keeps running when enabled. Something to try later on.
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ericy

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Re: DNS relay stops working.
« Reply #4 on: November 21, 2018, 10:28:11 AM »

No, disabling DNS relay only means that the router will not be the proxy for DNS between the internet and your devices. So if you disable DNS relay, it means that your devices will get DNS either from your ISP or if you input custom DNS, this will appear on your devices.

Has a factory reset been performed to see if DNS Relay keeps running when enabled. Something to try later on.

Yeah, but it was the proxy for DNS that stopped working.  The router simply stopped responding to requests - going directly to the ISP did work, so the basic connectivity was still fine.

Haven't tried the reset - I got the thing new 6 weeks ago, so it seems unlikely that this would help.  The main thing I did when I got it was to update the firmware to 3.10.
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FurryNutz

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Re: DNS relay stops working.
« Reply #5 on: November 21, 2018, 10:30:13 AM »

How was the new FW applied?
Did you follow this?
Link> >FW Update Process
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ericy

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Re: DNS relay stops working.
« Reply #6 on: November 21, 2018, 11:36:43 AM »

How was the new FW applied?
Did you follow this?
Link> >FW Update Process

I just used the web UI to check for and apply updates using Firefox as a browser.  The thing was basically new, so I didn't try and save/restore any settings.  I don't really remember what the state of the thing was after the update, but I would have configured as required.
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FurryNutz

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Re: DNS relay stops working.
« Reply #7 on: November 21, 2018, 03:06:38 PM »

One this to try if you want to, do a factory reset and setup from scratch and see if enabling DNS Relay still fails. You can also try a downgrade of FW as well. Possible this came in with the new update.
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