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DNS Issues

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Grafter
Posts: 26
Thanks: 7
Registered: ‎22-06-2020

DNS Issues

We got our Hub One router and a bump up to FTTC a couple of weeks ago after having been happily using ASDL2+ and a third party NETGEAR router for years. Since then I have been having intermittent problems with doing DNS lookups. When it happens it affects all devices on the network, and the only way to get it back is to reset the router. 

Our router is on the latest firmware version (as far as I can tell: 4.7.5.1.83.8.263)

One thing I have noticed in common with the times this has happened is that is immediately after i come off a Zoom call. In at least one case I was connected to VPN when I started the call, but not when I finished, and its possible (or even likely?) this was the case the other times as well.

The last time it happened I noticed, looking at the router logs, that just before it did the router had blocked a large number of attempts to connect to remote administration ports (messages like "IN: BLOCK [16] Remote administration")

I have seen these threads:

https://community.plus.net/t5/My-Router/HubOne-firmware-issue-with-DNS/td-p/1509006

and
https://community.plus.net/t5/My-Router/Router-DNS-issue-Hub-One/td-p/1701998

 

But I'm not convinced the problem is the same (happy to shift this over to those threads if someone thinks it is) as I can `nslookup` neither via forwarding:

nslookup bbc.co.uk 192.168.1.254
Server:  dsldevice.lan
Address:  192.168.1.254

DNS request timed out.
    timeout was 2 seconds.
DNS request timed out.
    timeout was 2 seconds.
*** Request to dsldevice.lan timed-out

 

nor directly to the plusnet DNS servers:

nslookup bbc.co.uk 212.169.6.9
DNS request timed out.
    timeout was 2 seconds.
Server:  UnKnown
Address:  212.169.6.9

DNS request timed out.
    timeout was 2 seconds.
DNS request timed out.
    timeout was 2 seconds.
DNS request timed out.
    timeout was 2 seconds.
DNS request timed out.
    timeout was 2 seconds.
*** Request to UnKnown timed-out

 

But I can if I use the google DNS:

nslookup bbc.co.uk 8.8.8.8
Server:  dns.google
Address:  8.8.8.8

Non-authoritative answer:
Name:    bbc.co.uk
Addresses:  2a04:4e42:400::81
          2a04:4e42::81
          2a04:4e42:600::81
          2a04:4e42:200::81
          151.101.0.81
          151.101.192.81
          151.101.128.81
          151.101.64.81

 

The above  was on the Windows cmd.exe shell. The same behavior happens with `nslookup` on a WSL Ubuntu bash shell, but unexpectedly I *can* do the lookup using `dig`:

~$ dig +trace bbc.co.uk

; <<>> DiG 9.10.3-P4-Ubuntu <<>> +trace bbc.co.uk
;; global options: +cmd
.                       3600    IN      NS      FWDR-10.FWDR-6.FWDR-159.FWDR-212.
.                       3600    IN      NS      FWDR-9.FWDR-6.FWDR-159.FWDR-212.
;; Received 177 bytes from 192.168.1.254#53(192.168.1.254) in 5 ms

bbc.co.uk.              153     IN      A       151.101.192.81
bbc.co.uk.              153     IN      A       151.101.128.81
bbc.co.uk.              153     IN      A       151.101.0.81
bbc.co.uk.              153     IN      A       151.101.64.81
bbc.co.uk.              299     IN      NS      ns3.bbc.co.uk.
bbc.co.uk.              299     IN      NS      ns4.bbc.co.uk.
bbc.co.uk.              299     IN      NS      ns3.bbc.net.uk.
bbc.co.uk.              299     IN      NS      ns4.bbc.net.uk.
;; Received 182 bytes from 212.159.6.10#53(FWDR-10.FWDR-6.FWDR-159.FWDR-212) in 12 ms


We have the following devices on our network:

2x Windows Laptops

2x Android Phones

1x iPad

1x Chromecast 2nd Gen

1x AirstreamS200 Bluetooth/WiFi speaker.

 

52 REPLIES 52
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Grafter
Posts: 26
Thanks: 7
Registered: ‎22-06-2020

Re: DNS Issues

Happened again. This time nslookup specifying 212.159.6.10 did work. 

 

I also noticed the DNS getting slow and tempromental before it eventually gave out completely while I was on a video call. 

 

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Plusnet Help Team
Plusnet Help Team
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Registered: ‎21-04-2017

Re: DNS Issues

Thanks for getting in touch @IanSudbery I'm sorry for the problems with your connection. I think that the DNS issues are more of a symptom rather than a cause. I've tested your line tonight and the tests are showing a bridge tap which is generally as a result of faulty internal wiring although it may be caused by external wiring on the line too.

Bridge taps normally don't cause an issue with standard broadband compared to fibre so this may be why you didn't have an issue before you upgraded. I'd recommend plugging your router into the test socket as explained Here as this should rule out any issues with internal wiring including the faceplate of the master telephone socket. 

Once you've plugged your router into the test socket I'd advise reporting a fault online at http://faults.plus.net posting back after so we can retest your line and arrange an engineer visit to investigate further if the bridge tap is still present.

In addition to this because the bridge tap after all may be a red herring, are all your devices wireless or do you have any laptops or computers plugged directly into your router using an ethernet cable that's having issues? If they're wireless I'd recommend moving some devices onto the 5GHz wireless frequency.

If this post resolved your issue please click the 'This fixed my problem' button
 Anoush Mortazavi
 Plusnet Help Team
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Grafter
Posts: 26
Thanks: 7
Registered: ‎22-06-2020

Re: DNS Issues

Thanks for getting back @Gandalf . We are in a modern apartment building that doesn't have BT/Openreadch faceplates, so it might be hard to locate the master socket (there are 5 sockets in the apartment!), but I will see what I can do. Should I move the router to each in turn and  submit a report on faults.plus.net after each move?

Would a bridge tap not prevent the router from syncing entirely? Its odd that the google DNS still responds fine, and I can connect to the internet if I force my laptop to use that DNS rather than the auto configured one. 

I did try connecting to 5GHz when this last happened, to no avail - I will try weird next time. Again, I'd find it odd if it were a WiFI issue though, cause it works fine with the Google DNS. 

Also if I've got a connection already open when it happens, on a video call, or streaming for example, that will continue to work fine.

 

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Seasoned Hero
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Re: DNS Issues

@IanSudbery 

The idea when reporting a fault is to plug your hub in to the test socket and leave it connected in that way until Plusnet have checked out the line, so you can't simply keep moving your hub and report a fault. You will still get broadband, be it possibly degraded, if you have a bridge tap on your line.

It might be worth removing the face plates and looking in behind at the cabling. They will be interconnected in one of two ways.

1 Star Connection.

If they are star connected then four of the sockets will only have one cable connected to it. These are the extensions. The fifth will be the master socket and will have the four extension cables plus the incoming telephone cable connected. This is the worst possible combination and should be changed to a BT Master Socket with a filtered faceplate to filter off the extensions.

Alternatively have you looked around to see if there's a mysterious junction box anywhere where all these extensions are star connected with the incoming telephone cable? If so again this should be converted into a Master socket. If all the extensions only have one cable then there is definitely a junction box somewhere.

2. Daisy Chained connection.

In this configuration each extension is daisy chained as per the description. The last in the line will only have one cable going to it, all the others will have two. If you find the last one in the chain it might give you a clue from the physical layout the sequence in which they are connected. All the others will have two cables. All that you can do in this case is look at the cable. It is quite possible that the incoming cable is different in some way, be it the core markings or even the colour of the cable sheath. If you can find one cable that is unique then you have found where your master socket should be located.

This should then ideally be converted to a filtered master socket and the extensions filtered off.

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Plusnet Help Team
Plusnet Help Team
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Registered: ‎21-04-2017

Re: DNS Issues

Thanks for getting back to me @IanSudbery It won't be easy to rule out any internal wiring if you don't have an Openreach master telephone socket in that case. A bridge tap generally doesn't cause total loss of service, it can cause a variety of odd issues that we can't detect other than that the bridge tap is showing.

As an example, my parents had standard broadband for many years without issues until fibre came to their village a few years ago and since upgrading they had a lot of connection issues, sometimes the broadband connection wasn't even fully dropping, but things like streaming would just lag to the point it was unwatchable.

After some head scratching we called out an engineer and they identified the house was star-wired. Slightly different to your situation but still similar, their house had 3 master sockets all with 'test sockets'. Anyway the engineer fitted a brand new master to isolate the suspect wiring and since then the problem was resolved.

I can't guarantee that the bridge tap in your case is the problem, but I'm certain at this stage it's a good place to start. If you don't have a removable faceplate on your telephone sockets, personally I'd just try connecting your router into each one in turn and see if you have the same issues you've got now.

If you do have issues with each socket, I'd then recommend raising a fault so we can arrange an engineer.

Having said that, I've just read what you said about it working fine with Google DNS. Does this mean that you don't have any problems at all with your service when you configure your devices to use Google's DNS but you do with ours? If that's the case the issue may be the router as that'd be responsible for giving your devices the correct DNS if the devices are set to automatically obtain the DNS servers that is.

If this post resolved your issue please click the 'This fixed my problem' button
 Anoush Mortazavi
 Plusnet Help Team
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Grafter
Posts: 26
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Registered: ‎22-06-2020

Re: DNS Issues

Hi @Gandalf yes, when we are in a fault state, configuring the device to use google's DNS means the device works fine - 25Mb/9Mb. Unfortunately this is not possible on all devices, or we'd probably just make that change and be done with it. Its also the case that if one of the devices happens to be connected to VPN (and so using the remote network's DNS rather than plusnet's) when the fault develops, the connection for that device continues to be absolutely fine (25Mb/9Mb). To me. this doesn't suggest a problem with the wiring, but of course, I'm not an expert.

I also tried connecting via wired today when it happened - same as wireless. 

One more piece of intelegence - today when I tried to test the DNS lookup, `dig` could do the look up if I ran `dig +trace bbc.co.uk`, but not if I just ran `dig bbc.co.uk`.

 

These symptoms seem similar to the other issues I referenced in my original post. 

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Plusnet Help Team
Plusnet Help Team
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Registered: ‎21-04-2017

Re: DNS Issues

Hi @IanSudbery I agree, I think the bridge tap may be a red herring. I'm sending you a replacement router now you should receive within the next 3 to 5 working days. Could you let me know how it goes once you've got it?

If this post resolved your issue please click the 'This fixed my problem' button
 Anoush Mortazavi
 Plusnet Help Team
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Grafter
Posts: 26
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Registered: ‎22-06-2020

Re: DNS Issues

@Gandalf I'll let you know how it goes. 

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Grafter
Posts: 26
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Registered: ‎22-06-2020

Re: DNS Issues

@Gandalf 

 

Router arrived, so when it happened today, I switched them over. I will let you know one way or the other. 

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Grafter
Posts: 26
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Registered: ‎22-06-2020

Re: DNS Issues

Just had the same problem from the new router. Exactly the same symptoms. I know that bobpullen was looking at this problem with others that have this problem (I havn't tagged them in because I don't know if that would be rude).

 

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Plusnet Help Team
Plusnet Help Team
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Registered: ‎21-04-2017

Re: DNS Issues

I've raised this to our products team (Generally Bob as he owns the Hardware side of things) internally for further investigation. I'll post back when I know more which should be within the next 3 working days.

If this post resolved your issue please click the 'This fixed my problem' button
 Anoush Mortazavi
 Plusnet Help Team
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Community Gaffer
Community Gaffer
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Re: DNS Issues

@IanSudbery I concur that this doesn't seem to be related to some of the other threads you've linked to. There's a distinct difference in that look-ups directly to the Plusnet DNS resolvers also seem to be failing.

Reading through your symptoms, there is one particular difference that I can't shake that separates lookups to the Plusnet DNS caches versus Google's. Our caches are behind an IP ACL so will only allow lookups from Plusnet IP ranges. Google's will allow access from anywhere.

I assume your VPN is client-specific? i.e. it is only ever running on a single machine, rather than at a router/network level? I also assume you were able to use the VPN without issue when running with the Netgear?

@Gandalf can we try routing Ian's connection over the L2TP network please to see if it helps? I notice they are currently on one of the IP ranges we've had problems with previously, and I'd like to rule that out before we investigate any further.

Bob Pullen
Plusnet Product Team
If I've been helpful then please give thanks ⤵

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Plusnet Help Team
Plusnet Help Team
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Re: DNS Issues

Thanks for the assist @bobpullen 

@IanSudbery is now a proud owner of a static IP (free of charge and potentially temporarily of course).

If this post resolved your issue please click the 'This fixed my problem' button
 Anoush Mortazavi
 Plusnet Help Team
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Grafter
Posts: 26
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Registered: ‎22-06-2020

Re: DNS Issues

Thanks for the reply @bobpullen - whether or not we can lookup via directly specifying the plusnet server seems intermittent - sometimes when DNS is not working we can, sometimes when DNS is not working we can't.

If I do `dig +trace` I can do a lookup, so it seems the servers will respond to me under some circumstances. 

The VPN is indeed client specific. I wasn't connected and I hadn't been connected recently when this happened yesterday.