DNS Servers – A Lesson Learnt

The internet in our house hasn’t been working well for a while now. It works fine when you are connected, and throughput tests show, stable, high speed upstream and down. But leave your device alone for a while and it may struggle to reconnect. Turn a tablet on next to a laptop, and they both lose the connection. Even the wired connection devices were losing the network.

For those with a short attention span I can report that the problem is now solved. If you wish to know more, and find out how, then please read on.

This problem has been steadily developing. It used to be sporadic and last Thursday it became a permanent situation!  There was no connectivity for all devices for over half an hour. BT were not reporting a fault, and our Home Hub 3 still had the Blue, connected, lights on.

Question MarkI am a tester, so I always ask “What has changed? What made this happen?

Thinking back, on Wednesday I received an e-mail from Amazon asking me to upgrade the software on my old Kindle. We both have 2 old Kindles. I charged them up. Downloaded the new software and updated them. All was fine.

A few days before I had bought 2 new Raspberry Pi 3 computers. These come with Ethernet and on board WiFi. So I tested both. All was fine.

I suppose I have a somewhat more extensive home network than many. We have a BT Broadband Infinity 2 connection and a BT Home Hub 3. The Home Hub is connected into a switch, and also connected is a Netgear Wireless Router. We have a separate wireless router because of the enforced positioning of the BT Home Hub, near the phone socket at a front corner of the house, does not provide a good wireless signal to the whole house, so we have positioned a separate Netgear wireless router more centrally. It is also a much better wireless router, but that is by the by.

BC Network

I am sure that this setup is not actually that unusual. The Home Hub 3 has some limitations, like only having one gigabit connection. Whereas the rest of our network is all gigabit. The only setup change that we have made is to disable the WiFi on the Home Hub 3.

Where we tend to depart from the usual is that we do have a lot of devices connected. Although I suspect that this is in no way extraordinary. This is becoming the norm in the modern connected and ‘always on‘ home. So we have desktop computers, laptops, phones & kindles. There is PC stuff, like printers and NAS. And finally some home entertainment connections; media PC, satellite box, smart TV, & remote control. I also have a number of Raspberry Pi computers. 17 all told. These are not all connected, but have been, and some WiFI dongles that I can use with the Raspberry Pis.

I added this up, and including guests who had recently visited, I came to the grand total of 74 different connections through our Home Hub 3 in the recent past.  This is probably a lot.

TelephoneOn Saturday I bit the bullet and called BT to report the fault!  This is always a painful process. It takes hours on the phone. You are treated like a complete idiot. And as with all 3 calls on Saturday the problem went unresolved. I was actually cut off with all 3 calls. It seems to me that there is a 25 minute time limit on a call. If your problem is not solved in that time you are just cut off. Even though, all 3 times, they had my number, I was not rung back. I call that ‘customer disservice’. You may have a different name for it.

The upshot was that after the line testing, all of the Agents pronounced that my connection was fine. But we still couldn’t view webpages

However, one question all 3 agents asked was “How many devices do you have connected?”  Now I was saying 20, or 30. Actually I should have said 100+. I did wonder why this was relevant.

My last resort was to search the internet – maybe this should have been my first?. There I found a few comments about Home Hub 5 not working properly with a large number of connections, and an obscure link about the quality of the BT DNS servers, and an alternative solution using Google.

I began to piece things together. We have a large number of connections. The actual error we were getting, which I had reported to BT, was ‘DNS_Probe_Finished_No_Internet‘.

Now call me old fashioned, but here were all the clues. The article about the BT DNS servers also mentioned switching to use the Google DNS servers . Unfortunately this setting can’t be changed on the BT Home Hub 3. It is hardwired to use the BT DNS servers. So you have to configure each individual device on your network. Every computer, phone and tablet that can be changed – about 40 devices in all! And this isn’t so straight forward on some Android devices!

Of course, begin a good tester, I changed just one, and waited to see what happened …

About half an hour later, an unchanged tablet failed to connect, whilst my changed laptop kept working. There was evidence of success. So we changed all of the devices that were to hand – 10 so far. And to date we have not had a recurrence of the DNS failure. Yey 🙂

I ran 4 changed devices, sitting next to each other on the kitchen table, to check that everything was still working. They all worked just fine. Previously this had not bee possible.

However, as a good tester, I know it has been less than 24 hours, that this may only be a temporary fix, and that further problems may lie headed. In the meantime though, we will luxuriate in a return to speedy and stable internet access across our many connected devices.

And if anyone from BT ever reads this then here is a personal plea,

Fix your DNS servers, fix your Hubs, update your help desk scripts to cover this topic, stop cutting callers off after 25 minutes, and if you do cut them off, have the courtesy to ring them back!