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DNS gone down

Community Veteran
Posts: 18,023
Thanks: 1,687
Fixes: 20
Registered: ‎06-11-2007

DNS gone down

Now here`s a funny story, to tell it is a must....
At 19:56 tonight 6 December 2009, my wife yelled out from the next room, "lost the internet".... so I checked, and it seemed OK on my laptop... I did a My broadband speed test, and it gave the result Download speed 1390 and upload 359.... tried to do one on www.speedtest.net and it could not pass the latency test. !  hmm... so I checked a few of my favourite/bookmarks, including my blogsite and my website..... "Problem loading page" message.... so at 20:03, I phoned Plusnet CSC, and got the usual "all our agents are busy, messages,,  for about 5 minutes, then someone answered, and I told him lost the internet..... ah, says he..... we have a DNS problem.... access your router stats and tell me what DNS you are on....so I told him
  Preferred DNS Server : 212.159.6.9
Alternate DNS Server : 212.159.6.10
Ah yes, that is the one we have a fault on...... power down for half an hour and see if it is ok then....
Nothing else I can do?  no says he.... except wait....
FIne, says I...
so Thought .... I know what I`ll do, I`ll tell my sad tale to the rest of the Plusnet community,,.... cos even though I have lost my internet.because a DNS has gone down, I can still access the forum.... ? ? ? ?  Hm,mmmm
12 REPLIES
Community Veteran
Posts: 18,023
Thanks: 1,687
Fixes: 20
Registered: ‎06-11-2007

Re: DNS gone down

Update on my last..... didn`t do a thing.... except post that story... and it is back working again.... well done Plusnet staff, for a speedy recovery....  Smiley Smiley Smiley
pierre_pierre
Grafter
Posts: 19,757
Registered: ‎30-07-2007

Re: DNS gone down

cant be bothered to find it but they have two DNS servers as you say, one in on a newer software and seems to work OK, they will move the other one over that had an update of a "Secure" software that didnt work, that info is about two days old
pierre_pierre
Grafter
Posts: 19,757
Registered: ‎30-07-2007

Re: DNS gone down

Community Veteran
Posts: 18,023
Thanks: 1,687
Fixes: 20
Registered: ‎06-11-2007

Re: DNS gone down

YAY ! pierre.... that was supposed to happen on the 3rd in the morning.... so it has taken 3.5 days to break ! ! ! not to worry,,,,, it is working ok now ! !  Cheesy
pierre_pierre
Grafter
Posts: 19,757
Registered: ‎30-07-2007

Re: DNS gone down

its a matter of luck which one you get, see the Doctors surgery thread to which you replied
VileReynard
All Star
Posts: 11,191
Thanks: 305
Fixes: 11
Registered: ‎01-09-2007

Re: DNS gone down

Do Plusnet have a backup DNS which could be kicked into action every time the current setup fails?
Quote
Date/Time  	Facility  	Severity  	Message
Dec 6 19:55:23 user warn dnsprobe[874]: dns query failed
Dec 6 19:55:25 user warn dnsprobe[874]: dns query failed
Dec 6 19:55:27 user warn dnsprobe[874]: dns query failed
Dec 6 19:55:59 user warn dnsprobe[874]: dns query failed
Dec 6 19:56:01 user warn dnsprobe[874]: dns query failed
Dec 6 19:56:03 user warn dnsprobe[874]: dns query failed
Dec 6 19:56:35 user warn dnsprobe[874]: dns query failed
Dec 6 19:56:37 user warn dnsprobe[874]: dns query failed
Dec 6 19:56:40 user warn dnsprobe[874]: dns query failed
Dec 6 19:57:12 user warn dnsprobe[874]: dns query failed
Dec 6 19:57:14 user warn dnsprobe[874]: dns query failed
Dec 6 19:57:16 user warn dnsprobe[874]: dns query failed
Dec 6 19:57:48 user warn dnsprobe[874]: dns query failed
Dec 6 19:57:50 user warn dnsprobe[874]: dns query failed
Dec 6 19:57:52 user warn dnsprobe[874]: dns query failed
Dec 6 19:58:24 user warn dnsprobe[874]: dns query failed
Dec 6 19:58:26 user warn dnsprobe[874]: dns query failed
Dec 6 19:58:28 user warn dnsprobe[874]: dns query failed
Dec 6 19:59:00 user warn dnsprobe[874]: dns query failed
Dec 6 19:59:02 user warn dnsprobe[874]: dns query failed
Dec 6 19:59:04 user warn dnsprobe[874]: dns query failed
Dec 6 19:59:12 user debug syslog: ifconfig wl0 > /var/hwaddr
Dec 6 19:59:12 user debug syslog: wlctl channel > /var/curchannel

Dec 6 19:59:36 user warn dnsprobe[874]: dns query failed
Dec 6 19:59:38 user warn dnsprobe[874]: dns query failed
Dec 6 19:59:40 user warn dnsprobe[874]: dns query failed
Dec 6 20:00:12 user warn dnsprobe[874]: dns query failed
Dec 6 20:00:14 user warn dnsprobe[874]: dns query failed
Dec 6 20:00:16 user warn dnsprobe[874]: dns query failed
Dec 6 20:00:48 user warn dnsprobe[874]: dns query failed
Dec 6 20:00:50 user warn dnsprobe[874]: dns query failed
Dec 6 20:00:52 user warn dnsprobe[874]: dns query failed
Dec 6 20:01:24 user warn dnsprobe[874]: dns query failed
Dec 6 20:01:26 user warn dnsprobe[874]: dns query failed
Dec 6 20:01:28 user warn dnsprobe[874]: dns query failed
Dec 6 20:02:00 user warn dnsprobe[874]: dns query failed
Dec 6 20:02:02 user warn dnsprobe[874]: dns query failed
Dec 6 20:02:04 user warn dnsprobe[874]: dns query failed
Dec 6 20:02:36 user warn dnsprobe[874]: dns query failed
Dec 6 20:02:38 user warn dnsprobe[874]: dns query failed
Dec 6 20:02:40 user warn dnsprobe[874]: dns query failed
Dec 6 20:03:12 user warn dnsprobe[874]: dns query failed
Dec 6 20:03:14 user warn dnsprobe[874]: dns query failed
Dec 6 20:03:16 user warn dnsprobe[874]: dns query failed
Dec 6 20:03:48 user warn dnsprobe[874]: dns query failed
Dec 6 20:03:50 user warn dnsprobe[874]: dns query failed
Dec 6 20:03:52 user warn dnsprobe[874]: dns query failed
Dec 6 20:04:24 user warn dnsprobe[874]: dns query failed
Dec 6 20:04:26 user warn dnsprobe[874]: dns query failed
Dec 6 20:04:28 user warn dnsprobe[874]: dns query failed
Dec 6 20:05:00 user warn dnsprobe[874]: dns query failed
Dec 6 20:05:02 user warn dnsprobe[874]: dns query failed
Dec 6 20:05:04 user warn dnsprobe[874]: dns query failed
Dec 6 20:05:36 user warn dnsprobe[874]: dns query failed
Dec 6 20:05:38 user warn dnsprobe[874]: dns query failed
Dec 6 20:05:40 user warn dnsprobe[874]: dns query failed
Dec 6 20:06:12 user warn dnsprobe[874]: dns query failed
Dec 6 20:06:14 user warn dnsprobe[874]: dns query failed
Dec 6 20:06:16 user warn dnsprobe[874]: dns query failed
Dec 6 20:06:48 user warn dnsprobe[874]: dns query failed
Dec 6 20:06:50 user warn dnsprobe[874]: dns query failed
Dec 6 20:06:52 user warn dnsprobe[874]: dns query failed
Dec 6 20:07:24 user warn dnsprobe[874]: dns query failed
Dec 6 20:07:26 user warn dnsprobe[874]: dns query failed
Dec 6 20:07:28 user warn dnsprobe[874]: dns query failed
Dec 6 20:08:00 user warn dnsprobe[874]: dns query failed
Dec 6 20:08:02 user warn dnsprobe[874]: dns query failed
Dec 6 20:08:04 user warn dnsprobe[874]: dns query failed
Dec 6 20:08:36 user warn dnsprobe[874]: dns query failed
Dec 6 20:08:38 user warn dnsprobe[874]: dns query failed
Dec 6 20:08:40 user warn dnsprobe[874]: dns query failed
Dec 6 20:09:12 user warn dnsprobe[874]: dns query failed
Dec 6 20:09:14 user warn dnsprobe[874]: dns query failed
Dec 6 20:09:16 user warn dnsprobe[874]: dns query failed
Dec 6 20:09:48 user warn dnsprobe[874]: dns query failed
Dec 6 20:09:50 user warn dnsprobe[874]: dns query failed
Dec 6 20:09:52 user warn dnsprobe[874]: dns query failed
Dec 6 20:10:24 user warn dnsprobe[874]: dns query failed
Dec 6 20:10:26 user warn dnsprobe[874]: dns query failed
Dec 6 20:10:28 user warn dnsprobe[874]: dns query failed
Dec 6 20:10:59 user notice dnsprobe[874]: Switching Back To Primary DNS server

Community Veteran
Posts: 3,789
Registered: ‎08-06-2007

Re: DNS gone down

AFAIK they have DNS servers on four IPs (but probably loadbalanced 8-12 of them)
212.159.13.49
212.159.13.50
212.159.6.9
212.159.6.10

I think that's correct, but from memory so don't quote me.
B.
jnwright
Grafter
Posts: 281
Thanks: 1
Registered: ‎05-04-2007

Re: DNS gone down

I use DNSBench  to check on a large number of DNS servers obtainable here.
As you can see the PN ones are 100% reliable normally and the Opendns ones are slightly slower.  In windows you can have several servers.  I normally have 5 on my static IP desktop
212.159,6.9
212.159.6.10
212.159.13.49
212.159.13.50
192.168.1.1 (my router)
The first and second are normally suplied by PN to the router and are passed on to any devices getting their IP by DHCP.  I have interleaving on and a PN cached DNS reply usually takes about 60ms.
It is interesting to note that 212.159.6.9 and 212.159.13.49 both come up with the name cdns01.plus.net and, 212.159.6.10 and 212.159.13.50 both come up with cdns02.plus.net when using tracert or nslookup of their ip number, but both cdns01.plus.net and cdns02.plus.net come up with "Non-existent domain" using an nslookup of their name.  Normally when multiple IPs are using the same domain name, several numerical ip addresses are returned by nslookup.  tracert cdns01.plus.net and tracert cdns02.plus.net both fail.
custos
Aspiring Pro
Posts: 315
Thanks: 49
Fixes: 2
Registered: ‎28-06-2007

Re: DNS gone down

I have been using the recently publicised Google Public DNS servers which seem to be working very well. The IP addresses of the servers is very easy to remember: 8.8.8.8 and 8.8.4.4
jnwright
Grafter
Posts: 281
Thanks: 1
Registered: ‎05-04-2007

Re: DNS gone down

I haven't found the Google servers to be quite as fast as the PN or Opendns DNS servers.
Community Veteran
Posts: 26,744
Thanks: 954
Fixes: 10
Registered: ‎10-04-2007

Re: DNS gone down

OpenDNS is OK providing you are using OpenDNS Deluxe which allows you to configure invalid names to return an error and not a false advertising based result. To quote from the DNS Benchmark conclusions:
Quote
One or more of this system's nameservers intercepts errors and redirects web browsers to a custom page in response to an invalid DNS lookup request.  (This is shown with an orange coloring of the nameserver IP address and descriptive text on the benchmark's "Nameserver" page.)  This behavior is typically used as a marketing maneuver to redirect mistaken web browser URL entries to the DNS provider's own advertising-laden marketing-related pages. The major ISPs Earthlink, Roadrunner and Comcast are known to be doing this. While this may be regarded as a useful service by some users, others object to the idea of not receiving an error in response to an erroneous request. Some free DNS server providers, such as OpenDNS, allow this behavior to be customized so that erroneous queries can be configured to return an error. Many responsible ISPs are also offering "opt-out" options to prevent advertising interceptions.
Recommended Actions:
If you feel that this marketing-driven behavior is unacceptable from a DNS nameserver, you may be able to configure the service to return errors. Otherwise, you are free to switch to any alternative high performance and high reliability nameservers that are properly returning errors in response to erroneous queries.
If you choose to configure the existing nameserver(s) to return errors, you can use this benchmark utility, at any time, to easily verify that the DNS behavior is what you expect and desire.

If the objective of adding OpenDNS or Google DNS servers is to act as a fallback to the Plusnet servers then I wouldn't have thought speed was as critical (in any case I suspect the fallback servers are more likely to be used for the uncached results (green bars)  and the speed difference in those isn't much). If you don't want to use a DNS server that lies you have a choice of paying $9.95/year for OpenDNS or using the free Google server. Not a difficult decision!
I'm using Treewalk which pretty obviously is near instantaneous for cached results (red bars).
jelv (a.k.a Spoon Whittler)
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Community Gaffer
Community Gaffer
Posts: 13,582
Thanks: 1,267
Fixes: 103
Registered: ‎04-04-2007

Re: DNS gone down

Quote from: shutter
YAY ! pierre.... that was supposed to happen on the 3rd in the morning.... so it has taken 3.5 days to break ! ! ! not to worry,,,,, it is working ok now ! !   Cheesy

We did have a problem with DNS Sunday evening, and it was at the site we did the work at last week. We're refraining from making any more DNS changes until we know exactly what caused the problems.
Quote from: jnwright
I haven't found the Google servers to be quite as fast as the PN or Opendns DNS servers.

I doubt that's ever going to change. Our caching DNS servers live in the same data centres as the edge routers your connections are terminated on so will be very quick to respond.
Quote from: Barry
AFAIK they have DNS servers on four IPs (but probably loadbalanced 8-12 of them)
212.159.13.49
212.159.13.50
212.159.6.9
212.159.6.10

Yep four virtual IPs that map to 8 physical machines I think (four per site). The server you're assigned is advertised by the edge routers/gateways using BGP. No matter which Virtual IP you use, you'll always hit the same data centre as can be seen by the load balancer hop in the following traces.
Quote
C:\Users\Bobby>tracert 212.159.13.49
Tracing route to cdns01.plus.net [212.159.13.49]
over a maximum of 30 hops:
  1    2 ms    1 ms    2 ms  gateway.anfield [192.168.1.254]
  2    29 ms    28 ms    34 ms  lo0-homesurf.thn-ag3.plus.net [195.166.128.81]
  3    28 ms    28 ms    29 ms  vl306.thn-gw1.plus.net [84.92.3.201]
  4    28 ms    28 ms    28 ms  te3-2.ptn-gw01.plus.net [212.159.1.53]
  5    26 ms    29 ms    28 ms  vl55.ptn-lb01.plus.net [212.159.2.124]
  6    29 ms    29 ms    29 ms  cdns01.plus.net [212.159.13.49]
Trace complete.

Quote
C:\Users\Bobby>tracert 212.159.13.50
Tracing route to cdns02.plus.net [212.159.13.50]
over a maximum of 30 hops:
  1    1 ms    2 ms    1 ms  gateway.anfield [192.168.1.254]
  2    29 ms    31 ms    30 ms  lo0-homesurf.thn-ag3.plus.net [195.166.128.81]
  3    29 ms    26 ms    28 ms  vl306.thn-gw1.plus.net [84.92.3.201]
  4    27 ms    31 ms    27 ms  te3-2.ptn-gw01.plus.net [212.159.1.53]
  5    30 ms    30 ms    29 ms  vl55.ptn-lb01.plus.net [212.159.2.124]
  6    29 ms    27 ms    29 ms  cdns02.plus.net [212.159.13.50]
Trace complete.

Quote
C:\Users\Bobby>tracert 212.159.6.9
Tracing route to cdns01.plus.net [212.159.6.9]
over a maximum of 30 hops:
  1    2 ms    1 ms    1 ms  gateway.anfield [192.168.1.254]
  2    29 ms    31 ms    28 ms  lo0-homesurf.thn-ag3.plus.net [195.166.128.81]
  3    29 ms    29 ms    28 ms  vl306.thn-gw1.plus.net [84.92.3.201]
  4    29 ms    29 ms    30 ms  te3-2.ptn-gw01.plus.net [212.159.1.53]
  5    27 ms    29 ms    29 ms  vl55.ptn-lb01.plus.net [212.159.2.124]
  6    29 ms    27 ms    29 ms  cdns01.plus.net [212.159.6.9]
Trace complete.

Quote
C:\Users\Bobby>tracert 212.159.6.10
Tracing route to cdns02.plus.net [212.159.6.10]
over a maximum of 30 hops:
  1    1 ms    2 ms    2 ms  gateway.anfield [192.168.1.254]
  2    31 ms    28 ms    44 ms  lo0-homesurf.thn-ag3.plus.net [195.166.128.81]
  3    29 ms    29 ms    30 ms  vl306.thn-gw1.plus.net [84.92.3.201]
  4    29 ms    28 ms    29 ms  te3-2.ptn-gw01.plus.net [212.159.1.53]
  5    29 ms    29 ms    29 ms  vl55.ptn-lb01.plus.net [212.159.2.124]
  6    27 ms    30 ms    30 ms  cdns02.plus.net [212.159.6.10]
Trace complete.

'ptn' represents one site, whereas 'pcl' represents the other. It's the ptn site that this work relates to and it's the ptn site we had the problems with on Sunday.

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