DNS Server

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Boac
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DNS Server

#1 Post by Boac » Thu Jul 02, 2020 7:45 pm

For a long time I have (lazily) used Google's DNS servers, but over the last couple of days noticed an occasional 'misfire' from them. I am using Open DNS at present. Anyone else had the same?

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Re: DNS Server

#2 Post by admin » Fri Jul 03, 2020 4:22 am

Our annual domain registration fees include all aspect of DNS server management. I can add, change & delete any records, as and when I care to.

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Re: DNS Server

#3 Post by Boac » Fri Jul 03, 2020 6:58 am

Has anyone noticed any 'misfires' with Google DNS servers?

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Re: DNS Server

#4 Post by Pontius Navigator » Fri Jul 03, 2020 7:32 am

How does one use a Google DNS server. What do you use it for? It's one of those network things I just take for granted.

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Re: DNS Server

#5 Post by Boac » Fri Jul 03, 2020 7:43 am

Unless you change the setting in your router, your router will almost certainly, by default, use your ISP's DNS service. I switched mine some years ago as Plusnet's DNS Server was noticeably slow. Goggle's servers (8.8.8.8. and 8.8.4.4.) have been absolutely fine since then until about 3 days ago. I have now switched to 'Open Dns' and 'normal service' has been restored.

In case you do not know, A DNS server (qv) translates "ops-normal.org" into the Domain name address for the domain or website which is 43.250.140.10 for O-N. It is obviously easier to remember ops-normal.org!!!

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Re: DNS Server

#6 Post by llondel » Fri Jul 03, 2020 8:21 pm

I use my own internal servers that will then connect to something on the outside world. They're not pointed at anything more specific than the root servers.

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Re: DNS Server

#7 Post by Boac » Fri Jul 03, 2020 8:23 pm

llondel - you've got an 'internal' DNS server? Never come across one of those apart from on a network. How does it translate a url to an IP?

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Re: DNS Server

#8 Post by llondel » Fri Jul 03, 2020 8:29 pm

Boac wrote:
Fri Jul 03, 2020 8:23 pm
llondel - you've got an 'internal' DNS server? Never come across one of those.
https://www.isc.org/bind/

Industry standard. I have three running inside my firewall and various machines will try any or all of them as needed. I don't strictly need three, but I wanted to find out how to do it so I set them up. Same for DHCP servers, most people just use whatever's in their router but I have a couple of them running because I wanted to figure out how to do it.

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Re: DNS Server

#9 Post by Boac » Fri Jul 03, 2020 8:56 pm

Never got into 'Bind'. Do you not still require to fetch data from other DNS servers to resolve O-N to its IP address, or does Bind do that itself?

I WAS trying to keep it fairly simple for PN and others (including me...) :))

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Re: DNS Server

#10 Post by llondel » Fri Jul 03, 2020 9:21 pm

It does fetch from outside, but DNS servers can be configured to fetch from a nominated upstream server or start at the top and work down. DNS servers also cache stuff for a while, so for frequently-used stuff it will rarely query outside.

If you use Google's server then it will probably be the one that goes and queries from the top down, although if someone else has asked for the same query recently then it probably has the answer cached.

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Re: DNS Server

#11 Post by Boac » Sat Jul 04, 2020 6:54 am

OK - so let's assume you need to access a URL you have never been to before, it is a 'new' one, not cached, but all 'in place' ie nameservers etc all correctly set - how is your system set to resolve the IP? Where does it 'go'? To a DNS server or not?

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Re: DNS Server

#12 Post by llondel » Sun Jul 05, 2020 5:17 am

It does a recursive look-up. Assuming it has no knowledge of any domain name, first it asks one of the root servers, which are fixed and known. From there it would ask for ".com" or ".uk". It would get an answer, whereupon it would go ask one of those servers, which would probably then tell it to go look at the next level server until it found either the authoritative server for the domain or at least one that had an answer cached. Next time it might not need to go as far as the root server if it already knows the com/uk/other top level domain. There's also a Time To Live attached to each look-up and after it expires, the local server will remove the relevant entry and so go look it up from scratch again. Stable stuff often has a TTL of a week.

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Re: DNS Server

#13 Post by Boac » Sun Jul 05, 2020 10:11 am

Boring for many, but interesting for me(!) I take it, from what you say, then that your BIND system goes direct to a root server and not through a 'public' nameserver?

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Re: DNS Server

#14 Post by G-CPTN » Sun Jul 05, 2020 11:25 am

Just had several minutes unable to connect with ops-normal.

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Re: DNS Server

#15 Post by llondel » Sun Jul 05, 2020 5:01 pm

Yes, my system would go directly to the root if it didn't have something already cached. If I asked a public nameserver then it would be the one to go visit a root server if it needed to.

There is the concept of being the authoritative server for a domain, as in, the server from which all others ultimately derive their information about that domain. For my domains, that happens to be the Linode servers, as can be discovered by doing a whois query (on Linux systems, anyway). I just did a trace on llondel.com, my puppy domain. It picked the F root server, f.root-servers.net (there are a bunch of them scattered around the world), which pointed it to a bunch of next-level servers for .com, from which it picked m.gtld-servers.net, which then pointed it at ns1.linode.com, which is marked as authoritative so that's where I got the answer.

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Re: DNS Server

#16 Post by G-CPTN » Thu Jul 23, 2020 1:37 pm

I am currently (as I write this @ 12:30) unable to connect to the internet.
Of course I am unable to check whether this is due to problems with my ISP (Talk-Talk) or with my router (which, it appears, is connected by WiFi to my computer).

It isn't a problem with the power supply.

Windows Network Diagnostics reports that the DNS server isn't responding - which doesn't mean anything to me.

I don't know whether it is a temporary outage or a 'permanent' failure.

I cannot check any online facility.

'Help' relies on the internet - so no help.

I cannot look up the telephone number of my ISP.

I cannot 'read the news'.

I think I will go out for a walk.

Update:- here I am @ 14:30, so 'it wasn't me'. Heard in the village that others were experiencing difficulty accessing t'internet.

Would it be a 'local' outage (don't suppose the others were with TT) or a regional problem?

One feels so helpless!

TalkTalk down.

More here.

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Re: DNS Server

#17 Post by Boac » Fri Jul 24, 2020 4:35 pm

This may be your problem


Thursday, July 23, 2020 3:42 PM
9 comments

Hopefully no one is injured, but it appears a fire at around midday caused Andrews and Arnold to issue a service status update for customers in the Newcastle, Durham and Carlisle area.

The problem was initially identified as a cluster of dropped lines with an update from BT around 1pm indicating that a fire has impacted a fibre node serving an area.

We don't know if this is a fire in a single head end exchange, thus affecting a number of satellite exchanges served by Openreach fibre, or whether this is a larger node affecting a number of exchanges. If we learn anything more we will update everyone.

Update 3:40pm It appears from around 2.30pm service was being restored, with power coming back on in the exchange building. As is normal after a power cut power is restored in steps to avoid a blunt switch on causing further issues, which means some services may have started working before others.

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Re: DNS Server

#18 Post by G-CPTN » Fri Jul 24, 2020 4:41 pm

Yes, thanks.

I just wish I had known that at the time.

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