Problem with DNS on rt2600ac

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DaveHamilton
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Re: Problem with DNS on rt2600ac

Unread post by DaveHamilton » Sun Jul 15, 2018 5:19 am

synpol wrote:
Sat Jul 14, 2018 10:32 pm
One more thing, do you use dual WAN setup with either failover or load balancing?
No. Single WAN here. Pretty standard in that regard.

synpol
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Re: Problem with DNS on rt2600ac

Unread post by synpol » Sun Jul 15, 2018 9:04 am

DaveHamilton wrote:
Sun Jul 15, 2018 5:19 am
synpol wrote:
Sat Jul 14, 2018 10:32 pm
One more thing, do you use dual WAN setup with either failover or load balancing?
No. Single WAN here. Pretty standard in that regard.
There is definitely something wrong with the way router handles DNS. I already have a ticket on my issue described earlier in this thread and the Synology support seems to acknowledged it. What would be nice to check is once this DNS issue happens (devices unable to resolve addresses), if the ping/trace commands is successful via router network tools GUI or ssh. My issue for instance is irrelevant of the device, it happens everywhere including on the router level. But it is a bit different issue related to dual wan DNS handling.

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Re: Problem with DNS on rt2600ac

Unread post by synpol » Fri Jul 20, 2018 1:48 am

My DNS bug described earlier in this thread has been confirmed by Synology and they promised to fix it. Basically in dual wan setup failover mode if you set the same DNS IP that you will also put in the interface check, router decides to handle those DNS requests via secondary interface (despite being failover...). Funny enough, if you kill internet on your secondary interface, all devices will lose DNS resolving ability as primary WAN is not taking over the DNS routing! Solution for the time being is to use a different set of DNS IP in interface check than the one set on the main connection tab.

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DaveHamilton
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Re: Problem with DNS on rt2600ac

Unread post by DaveHamilton » Fri Jul 20, 2018 5:25 pm

Mine was most definitely not related to dual WAN. My issue was having Network Center > Local Network > Primary DNS set to the address of the router (which is what I've aways done). It would work for a while, and then simply stop working until I went into the settings and changed something (like Internet > Connection > Manually configure DNS Server), which seemed to reset it for another 36-48 hours before it failed again.

Changing Local Network > Primary DNS to something other than the router address (like 1.1.1.1) solves it permanently, which tells me that the issue is the DNS server on the router stops answering after "a while"... like maybe it gets overloaded or something?

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DaveHamilton
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Re: Problem with DNS on rt2600ac

Unread post by DaveHamilton » Fri Jul 20, 2018 5:31 pm

I have submitted ticket 2046841 regarding this issue.

Voyager1
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Re: Problem with DNS on rt2600ac

Unread post by Voyager1 » Fri Aug 03, 2018 7:08 pm

I think I have the same issue. Some devices are unable to connect (requests result in timeout) and some keep on connecting (I'm suspecting local DNS cache for some running apps?). Anyway I'm going to try the change in Local Network > Primary DNS so that the RT2600ac doesn't serve as DNS server any longer.

By the way, do you have any update from the support ticket?

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DaveHamilton
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Re: Problem with DNS on rt2600ac

Unread post by DaveHamilton » Fri Aug 03, 2018 7:49 pm

Voyager1 wrote:
Fri Aug 03, 2018 7:08 pm
By the way, do you have any update from the support ticket?
Sadly, yes, I have "final" resolution on the ticket: "Unfortunately, I do not have a timeline for if or when this will be fixed."

Vintage Geek
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Re: Problem with DNS on rt2600ac

Unread post by Vintage Geek » Fri Aug 10, 2018 2:23 am

I've been running GRC's DNS Benchmark, and I've noticed lost DNS queries from the RT2600AC.
It is clearly the router as the I have it set up to directly query the DNS server as well as lots of other, and the ONLY errors come from the RT2600AC!

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Re: Problem with DNS on rt2600ac

Unread post by Babylonia » Fri Aug 10, 2018 9:05 am

Using the GRC DNS Benchmark, using the recommended DNS-servers, there should be no problem.
(Although not using a RT2600ac router, but RT1900ac).

Image


Actual test, in consideration of normal daily browsing data into account by "Google's DNS "Namebech" tool:
(Archived tool can be downloaded < HERE > ).

Result in my case using:
- 129.250.35.251 as primary DNS-server
- 216.146.35.35 as secondary DNS-server

See results < HERE >

Seems in this case the Google DNS server 8.8.4.4 is just a tiny bit more fast, than my actual used primary DNS-server.
(My System DNS-server in the case of Google benchmark tool, the approach of testing is a replica of 129.250.35.251 ).
I am using these DNS-servers already for a long time. It could be advisable now to just use another DNS-server.
Keep in mind it is always a snapshot. Maybe doing a test again tomorrow or in the evening can just give tiny differences.
By these tiny value differences, you shall not notice any differences in practice.

In past users did find great differences by using the provider recommended DNS-servers.
By errors of these DNS-servers and doing a test. Differences could be 1800 - 2000%

E.g. example < HERE > (hyperlink as by translation) ----> Result: < HERE >
(See also follow up message, as for result found a second time doing the test ---> now even 2000% ).

Just writing this message, there was a temporary 404 error of the ISP (Telfort) forum web-pages of my hyperlink.
They are working to have a new web-layout, so hyperlinks can be interrupted. Try again later if you met 404 errors.
RT1900ac / DS213j / DS415+ / DS218+ (at different locations).

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Re: Problem with DNS on rt2600ac

Unread post by Vintage Geek » Fri Aug 10, 2018 4:47 pm

Here is a screen capture of the typical errors I am seeing with GRC.
Note the red bar on the left of 192.168.77.1. That is my router. It is set to use 12.127.16.67 which you can see further down the list.
As you can see, the only DNS getting errors is the one requested from the router. It seems to be dropping DNS queries.

Image

Babylonia
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Re: Problem with DNS on rt2600ac

Unread post by Babylonia » Sat Aug 11, 2018 1:25 am

Vintage Geek wrote:
Fri Aug 10, 2018 4:47 pm
As you can see, the only DNS getting errors is the one requested from the router. It seems to be dropping DNS queries.
- Don't know if you are using Intrusion Prevention, but if so, stop it running.
- Use another Ethernet cable from router to your PC as for testing using GRC DNS Benchmark.
- Reboot router, reboot PC

If you test again, what does it bring to you?
RT1900ac / DS213j / DS415+ / DS218+ (at different locations).

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Re: Problem with DNS on rt2600ac

Unread post by Vintage Geek » Sat Aug 11, 2018 1:39 am

Babylonia wrote:
Sat Aug 11, 2018 1:25 am
Vintage Geek wrote:
Fri Aug 10, 2018 4:47 pm
As you can see, the only DNS getting errors is the one requested from the router. It seems to be dropping DNS queries.
- Don't know if you are using Intrusion Prevention, but if so, stop it running.
- Use another Ethernet cable from router to your PC as for testing using GRC DNS Benchmark.
- Reboot router, reboot PC

If you test again, what does it bring to you?
Not running Intrusion Protection, Cable is fine, HW has been rebooted.
No change.
I'll note that this doesn't happen every test run, but it does happen often. And only with the DNS through the router.
I'll run some more tests over the weekend.
Can someone else try this? Try a variety of DNS servers (not your ISPs designated one).

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akahan
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Re: Problem with DNS on rt2600ac

Unread post by akahan » Sat Aug 11, 2018 3:29 am

I use DNS Benchmark on my rt2600ac frequently, and have never seen such a problem.
If you run the benchmark while looking at CPU and memory usage in Network Center Status on the router, do the CPU or memory spike?
DS214play, DS216play, DS216, DS212J, DS414, DS816, rt2600ac

Connected
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Re: Problem with DNS on rt2600ac

Unread post by Connected » Sat Aug 11, 2018 7:18 am

Can someone else try this? Try a variety of DNS servers (not your ISPs designated one).
Not running it through VPN, right?
  • RT2600ac Primary interface OpenVPN: 20% DNS query loss
  • Direct to modem: nominal loss
  • RT2600ac Primary interface WAN: nominal loss
We live in a world of things that mostly sorta work.

Babylonia
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Re: Problem with DNS on rt2600ac

Unread post by Babylonia » Sat Aug 11, 2018 8:05 am

Vintage Geek wrote:
Sat Aug 11, 2018 1:39 am
Can someone else try this? Try a variety of DNS servers (not your ISPs designated one).
Tried several, but no problems.

Only by building a Custom list, and choosing a bad DSN server by purpose, I do get a faulty System DNS.
E.g. DNS 213.251.133.164 is used in below example / test.

Image
Vintage Geek wrote:
Sat Aug 11, 2018 1:39 am
.....Cable is fine.....
Be convinced about it. Today many bad quality cables are sold.
Not having the right specs and/or core wires by wrong material.
E.g. CCA = Copper Clad Aluminum instead of pure Copper core wires.

See YouTube movie as from < THIS point > ------> and < Actual test > (and see follow up).
"How To tell the difference between CCA and COPPER wire cable and FAKE ETHERNET cables"
RT1900ac / DS213j / DS415+ / DS218+ (at different locations).

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