DNS drop out

[#1]

Not sure if this is the correct place to mention this but . . . . .

Over the last few months we have been getting problems with DNS lookup. At first I thought it was my own setup but having done more checks - including switching 1 machine DNS lookup to 8.8.8.8, it seems that the problem is either at my router or with the Plusnet DNS servers. 

The problem only normally lasts a couple of minutes but was frustrating yesterday when I could not connect to Zoom.

Is anyone else noticing this.

David

[#2]

Moderators Note
This topic has been moved from Plusnet Feedback to My Router.

[#3]

@dallday are you using a Hub One ? and if so what is the firmware version ?

[#4]

Hi

yes - from the main screen "Plusnet Hub One | Software version 4.7.5.1.83.8.289.1.3 | Last updated 23/11/21"

Does it automatically update ?

Cheers

David

[#5]

@dallday  yes, it does automatically update but you have the latest firmware. There was an earlier version which had some DNS issues but they are resolved in the version you have.

including switching 1 machine DNS lookup to 8.8.8.8, it seems that the problem is either at my router or with the Plusnet DNS servers. 

What may be useful when/if it happens again is to switch the machine to use the Plusnet DNS servers directly . That will prove whether it is the Plusnet servers or the router which is causing the issues.

[#6]

Good suggestion I'll let you know next time we get an issue:)

[#7]

okay - it does seem to be my router.

I ran a script to use the linux dig command against the plusnet DNS servers (212.159.6.9 212.159.6.10 ) and my router - the results seem to suggest that the plusnet servers are working but my router was not responding.

Checked the router log and cannot see anything at about the time we were having problems

any idea or do I need a new router ?

[#8]

As I said earlier there was a problem with the DNS caching on older firmware but AFAIK the latest version (.289) resolved the problem. I'll give one of the product specialists a prod to review this thread.

[#9]

Yes, any issue should be resolved with the later firmware.

This said, the evidence does sound a tad damning 😕

I have seen one other instance like this that was ultimately caused by excess memory consumption, rather than anything specific to the DNS functionality. One of the side effects of lack of availalbe memory can be that DNS requests time out though.

The current memory consumption of @dallday's hub looks fine and lookups are working as I expect at the time of writing. The challenge here might be catching it when things are awry. Is it literally only a couple of minutes at a time that the problem's being experienced?

Unless I'm misaken, the router's been up for > 50 days, so it might be wise to powercycle it anyway.

[#10]

Will reboot the router

It is difficult to catch as  it only happens occasionally and is over in less than a minute

Have a script running on a Pi at once a minute and so far no failures - but saying that not sure I've seem any - sometimes get slow responses but not sure what causes it.

Will keep looking

David

[#11]

Is there a way to monitor the router performance from my computer ?

[#12]

Hi

It's been a while but I have managed to create a script to check my DNS results from various parts along the DNS chain. It checks once a minute and records the results as either all okay, or which parts of the DNS chain have failed. Script attached as  a text file - note it runs under linux

It checks
  the Plusnet dns 212.159.6.9 - reports "212.159.6.9"
  the plusnet dns 212.159.6.10 - reports "212.159.6.10"
  the router dns 192.168.1.1   - reports  "my router"
  the default settings just in case different - reports "local dns"

The latest issues occurred at 17:01 today and the is a extract from the log

2022-02-26-17-01-01 all okay
2022-02-26-17-02-01 all okay
2022-02-26-17-03-01 error  local dns
2022-02-26-17-04-01 error  my router local dns
2022-02-26-17-05-01 error  my router local dns
2022-02-26-17-06-01 error  my router local dns
2022-02-26-17-07-01 all okay
2022-02-26-17-08-01 all okay

at 17-03-01 it must have just started as the check on the router worked but then checking using the default dns, which is the same, failed. The the router dns failed for 3 minutes.

So it seems the update to the router has not stopped it happening completely.

Checking the full log shows it happened in frequently but if you are trying to load an internet page at the time it can be very frustrating.

David

[#13]

Thanks for getting back to me @dallday, I need you to monitor the connection and see if you have 3 or more drops in 72 hours so that I can progress this for you.

[#14]

@dallday - thanks, thats's really helpful (and pretty conclusive).

If you're able to provide a bunch of recent timestamps as to when the problem occurred, then I may be able to try and marry things up with some errant router activity. Failing that, I may abe able to organise some continuous monitoring of sorts.

Two questions:-

How it the Raspberry Pi connected (wired or wireless?)

Are you able to provide a description of your network setup/topology and summarise what you have connected to the network and how?

[#15]

Hi, been away for a bit so not got back on this.

The current monitoring Pi is a Pi Zero W and connects to the system via WIFI.

The current network setup is the Plusnet router is connected to a separate switch that handles our main desktops, mainly running Linux (3 machines) and a game machine running windows 10. I have also got a WiFi access point connected via Ethernet cable to the back of the house to provide additional WiFi support, and a separate WIFI access point connected via Ethernet cable to provide WiFi for an Oculus 2 headset.

There are a number of mobiles and tablets that connect to the WIFI.

I can move the DNS monitoring code onto a Pi that is directly connected to the plusnet hub if you think that might help, although the DNS dropouts I did notice was when I was on the main Linux computer which is directly connected to the switch via Ethernet cable.

Will take a look at the current logs and let you know.

David