Topic: [solved] DNS not working out of the blue, then it worked, then it didnt...

[joshAU]

Hi all.
Long time no post - 4 years I think!
My servers been behaving itself during that time, until yesterday.

Yesterday, I suddenly had no internet.
I could still ping external ip addresses, so I assume its DNS related.
 
Its running SME 8.2 in server-gateway mode, by the way.
I rebooted the server, and everything was back to normal.
A glitch I thought.

However, today its doing the same thing.
I logged into the server manager, and - foolishly I guess, decided to install some updates that were available.
Upon reconfigure and reboot, still no internet.

I restarted all the switches, and rebooted the server once again, and still no DNS.
I jumped on a windows pc and did an ipconfig - all info was correct.
I then statically set EXACTLY the same info (ip, subnet, gateway and DNS server) and hit ok, and viola!, internet.
I then switched it back to auto assign, and it continued to work.
Odd.

Then, a bit later this morning, no internet.
I checked ipconfig, and the wireless router for some reason was assigning me an ip in the wrong network... a 192.168.etc. rather than a 10.0.etc range.
Obviously the server was still up and running but for some reason decided to let the wireless router do the DHCP?
So I unplugged the wireless router and released/renewed the ip, and I'm back with working internet.

Any ideas as to why the DNS seems to have gone flakey?
Any suggestion of which logs to look into for further info?

I haven't done ANY changes to the server for ages - except the updates I put on after I noticed the issue had recurred today.

Any help greatly appreciated.
Thank you.
Josh

[Jáder]

I think your problem is TWO DHCP running.
Try to disable your ROUTER DHCP for now.

As far I know the quick DHCP to answer delivery IP to requester... so your router is answering quickly than server.

[byte]

Agree with Jader.  Did you perhaps update the WiFi router or factory reset the WiFi router maybe, hence turning on the WiFi router DHCP. 

[CharlieBrady]

Any ideas as to why the DNS seems to have gone flakey?

You've presented no evidence that DNS was flaky.

You've demonstrated that you have a problem with configuration and/or position in the network of a wireless router, which was misconfiguring other parts of your network. Leave your router switched off, or configure it correctly, and youf system will continue to work as it previously did.

[mmccarn]

Historically on my SME server DNS is the first thing to go if your hard drive fills up (learned the hard way when also "learning" about backup to USB drives...)

[joshAU]

Hi all.
Thanks for all the replies.
Apologies for the delay, no internet at home - NBN is getting connected today!

Thanks Jader.
Yes, I think it may have been an issue with the wireless router attempting to do the DHCP.
It was weird though, as the computer was set to auto ip, and had the correct details -ip, subnet, gateway and dns, so it didnt get those details from the wireless router.
It was only once I statically set exactly the same details that it started working, which is confusing.
Either way, its working now though.

Thanks byte.
Yep, I think you are both probably right.
But no, I hadn't done any changes to the router, nor had it reset to factory.

Thanks CharlieBrady.
Perhaps I used the wrong term.
I meant flakey as it the dns worked for years, then it stopped, started working after a reboot, and then 24 hours later dropped out again.
Stopped working as in I could ping the server, and external IP addresses, but not domain names.
But yes, it appears like the wireless router was the cause.

Thanks mmccarn.
Yes, I did check that, as I had similar issues several years ago when the drive filled up.

Well, thanks all for the input.
I'll mark this as closed/solved.
Appreciate all the advice.

 

[joshAU]

Well, it happened again, as I was on the internet - page cannot be found.... FFS
so, called my ISP, they did some tests and came back saying that several of their business NBN customers were experiencing the same issue, and they've logged a fault with NBN Co, the wholesaler.
Plugged a laptop directly into the NBN router, and it correctly assigned my static ip, but the gateway was not on the same subnet.. and I couldnt even ping an ip address.
Of course, as soon as I got through to support, the request time outs from the continuous ping I had going disappeared and the internet magically came back.
3 business days in a row... not really happy. grrrr.
On ADSL and ADSL2 virtually no drop outs or disconnects in 10 years.
Hopefully its just teething issues.
Either way, looks like it has absolutely nothing to do with SME server... which has been a great, reliable system. 
Thanks again for all your help.