Odd ball DNS behaviour

[#1]

Yet again when attempting to browse to google.co.uk I am getting "cannot connect" issues (no internet connection), even though I otherwise have no issues.  On investigating, I ran a nslookup query followed by a ping test.  I was somewhat surprised to see that the ping address resolution was different to all of the addresses listed by nslookup.
Looking further, I've found that repeated nslookups return different lists of IP addresses.  Is this to be expected or does it point to 'challenges' with PN's DNS servers?

Quote

#Microsoft Windows [Version 6.1.7601 #02/10/15-13:58:23.37 C:\Users\Kevin>nslookup Default Server:  dsldevice.lan Address:  192.168.1.254 > google.co.uk Server:  dsldevice.lan Address:  192.168.1.254 Non-authoritative answer: Name:    google.co.uk Addresses:  2a00:1450:4009:801::2003           212.56.71.230           212.56.71.249           212.56.71.227           212.56.71.251           212.56.71.212           212.56.71.229           212.56.71.216           212.56.71.223           212.56.71.234           212.56.71.240           212.56.71.208           212.56.71.241           212.56.71.238           212.56.71.219           212.56.71.245           212.56.71.218 > google.co.uk Server:  dsldevice.lan Address:  192.168.1.254 Non-authoritative answer: Name:    google.co.uk Addresses:  2a00:1450:4009:801::2003           212.56.71.25           212.56.71.49           212.56.71.50           212.56.71.35           212.56.71.55           212.56.71.45           212.56.71.24           212.56.71.29           212.56.71.20           212.56.71.40           212.56.71.39           212.56.71.54           212.56.71.59           212.56.71.44           212.56.71.34           212.56.71.30 > google.co.uk Server:  dsldevice.lan Address:  192.168.1.254 Non-authoritative answer: Name:    google.co.uk Addresses:  2a00:1450:4009:801::2003           212.56.71.230           212.56.71.249           212.56.71.227           212.56.71.251           212.56.71.212           212.56.71.229           212.56.71.216           212.56.71.223           212.56.71.234           212.56.71.240           212.56.71.208           212.56.71.241           212.56.71.238           212.56.71.219           212.56.71.245           212.56.71.218 > google.co.uk Server:  dsldevice.lan Address:  192.168.1.254 Non-authoritative answer: Name:    google.co.uk Addresses:  2a00:1450:4009:80a::2003           212.56.71.118           212.56.71.84           212.56.71.103           212.56.71.98           212.56.71.108           212.56.71.114           212.56.71.94           212.56.71.99           212.56.71.89           212.56.71.93           212.56.71.119           212.56.71.123           212.56.71.104           212.56.71.113           212.56.71.88           212.56.71.109 > google.co.uk Server:  dsldevice.lan Address:  192.168.1.254 Non-authoritative answer: Name:    google.co.uk Addresses:  2a00:1450:4009:80a::2003           212.56.71.104           212.56.71.123           212.56.71.89           212.56.71.114           212.56.71.99           212.56.71.119           212.56.71.113           212.56.71.93           212.56.71.118           212.56.71.94           212.56.71.103           212.56.71.109           212.56.71.108           212.56.71.98           212.56.71.88           212.56.71.84 > google.co.uk Server:  dsldevice.lan Address:  192.168.1.254 Non-authoritative answer: Name:    google.co.uk Addresses:  2a00:1450:4009:800::2003           212.56.71.119           212.56.71.123           212.56.71.94           212.56.71.109           212.56.71.98           212.56.71.84           212.56.71.118           212.56.71.108           212.56.71.93           212.56.71.99           212.56.71.89           212.56.71.103           212.56.71.114           212.56.71.104           212.56.71.88           212.56.71.113 > google.co.uk Server:  dsldevice.lan Address:  192.168.1.254 Non-authoritative answer: Name:    google.co.uk Addresses:  2a00:1450:4009:801::2003           212.56.71.104           212.56.71.123           212.56.71.89           212.56.71.114           212.56.71.99           212.56.71.119           212.56.71.113           212.56.71.93           212.56.71.118           212.56.71.94           212.56.71.103           212.56.71.109           212.56.71.108           212.56.71.98           212.56.71.88           212.56.71.84

Looking at a summary of the number of times an address was returned across the 7 queries is also interesting...

Quote

212.56.71.103 4           212.56.71.104 4           212.56.71.108 4           212.56.71.109 4           212.56.71.113 4           212.56.71.114 4           212.56.71.118 4           212.56.71.119 4           212.56.71.123 4           212.56.71.20 1           212.56.71.208 2           212.56.71.212 2           212.56.71.216 2           212.56.71.218 2           212.56.71.219 2           212.56.71.223 2           212.56.71.227 2           212.56.71.229 2           212.56.71.230 2           212.56.71.234 2           212.56.71.238 2           212.56.71.24 1           212.56.71.240 2           212.56.71.241 2           212.56.71.245 2           212.56.71.249 2           212.56.71.25 1           212.56.71.251 2           212.56.71.29 1           212.56.71.30 1           212.56.71.34 1           212.56.71.35 1           212.56.71.39 1           212.56.71.40 1           212.56.71.44 1           212.56.71.45 1           212.56.71.49 1           212.56.71.50 1           212.56.71.54 1           212.56.71.55 1           212.56.71.59 1           212.56.71.84 4           212.56.71.88 4           212.56.71.89 4           212.56.71.93 4           212.56.71.94 4           212.56.71.98 4           212.56.71.99 4

Is this normal behaviour or does it point to something amiss?
...yet again, opening a new browser session provides an immediate connection to google.co.uk without issue.

[#2]

Related to the problem last week?
From the office, using Open DNS or 8.8.8.8 it resolves sensibly ...

Quote

[tt]> server 8.8.8.8 Default server: 8.8.8.8 Address: 8.8.8.8#53 > www.google.co.uk Server: 8.8.8.8 Address: 8.8.8.8#53 Non-authoritative answer: Name: www.google.co.uk Address: 216.58.210.67 > server resolver2.opendns.com Default server: resolver2.opendns.com Address: 208.67.220.220#53 > www.google.co.uk Server: resolver2.opendns.com Address: 208.67.220.220#53 Non-authoritative answer: Name: www.google.co.uk Address: 216.58.210.67 >[/tt]

From home either Open DNS or Plusnet DNS give odd results ..

Quote

[tt]> www.google.co.uk Server:  cdns01.plus.net Address:  212.159.13.49 Non-authoritative answer: Name:    www.google.co.uk Addresses:  2a00:1450:4009:80d::2003           212.56.71.24           212.56.71.20           212.56.71.54           212.56.71.50           212.56.71.45           212.56.71.49           212.56.71.30           212.56.71.55           212.56.71.29           212.56.71.35           212.56.71.59           212.56.71.44           212.56.71.34           212.56.71.39           212.56.71.40           212.56.71.25 >                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         > www.google.co.uk Server:  resolver2.opendns.com Address:  208.67.220.220 Non-authoritative answer: Name:    www.google.co.uk Addresses:  2a00:1450:4009:801::2003           212.56.71.35           212.56.71.50           212.56.71.44           212.56.71.20           212.56.71.49           212.56.71.29           212.56.71.54           212.56.71.59           212.56.71.55           212.56.71.34           212.56.71.24           212.56.71.39           212.56.71.45           212.56.71.30           212.56.71.40           212.56.71.25 > [/tt]

Note IPv6 included!

[#3]

Also noticing DNS failures today. Didn't think too much of it at first, but now have noticed a few more big named sites not resolving (using Plusnet's DNS).
Have confirmed with a friend who is also using Plusnet, that he is seeing the same problem behaviour.
An example site that appears to be working fine with other ISPs, but not Plusnet: http://www.nasa.gov

[#4]

Quote from: monksteve

An example site that appears to be working fine with other ISPs, but not Plusnet: http://www.nasa.gov

I can reach that from Plusnet, but I'm using Open DNS name servers.

[#5]

Quote from: aesmith

Quote from: monksteve An example site that appears to be working fine with other ISPs, but not Plusnet: http://www.nasa.gov I can reach that from Plusnet, but I'm using Open DNS name servers.

Yeah, it's just Plusnet's DNS servers I'm seeing the problem on.

[#6]

Not seeing that problem here

[#7]

Whatever the problem was, it seems to have been rectified some time over the evening / night, for myself and a couple of Plusnet friends at least.

[#8]

I had the Nasa problem yesterday but  it works ok today.  I was just wondering how come they can control drone helicopters on a probe on mars when BTOR cant find a REIN source in a block of 8 shops.

[#9]

The funny thing is that when I look up say www.google.co.uk, over the Plusnet link then I get Plusnet host addresses returned, even from OpenDNS or even Google name servers.  Either Plusnet is re-writing the packet, or redirecting the query to their own DNS servers, or in some way the unrelated servers are being persuaded to return the Plusnet cache rather than the real thing.

[#10]

The Plusnet Google cache is the real thing. Not all DNS servers do it, e.g. 4.2.2.2 doesn't. You don't really encourage people to use your third-party DNS servers, which claim to be better and faster, with the drawback that you'll end up getting Google or Akamai content from further away.
There's no problem with the DNS responses in the first post, Plusnet disabled their Google cache a little while ago, but have evidently turned it back on, presumably after fixing the issue Apple computers had with it.

[#11]

ejs,
Thanks for advising that there is no issue with what I reported.  Can you please pint to some reference to the other matter you mention please?
Seeing numerous sets of different address sets (at the same time as seeing my periodic inability to connect on an other wise functioning link) looked odd and potentially relevant to the symptoms.

[#12]

Last week's Google issue is here: https://community.plus.net/forum/index.php/topic,144230.0.html
I'm not sure if there's any particular reference about third party DNS and CDNs (content distribution networks such as Akamai). In the past, using Google DNS or OpenDNS or others could have resulted in you accessing CDN content from servers further away than what has been installed at Plusnet. You can compare traceroutes, e.g. to static.bbci.co.uk
With Plusnet DNS, and Google DNS and OpenDNS
[tt]traceroute to static.bbci.co.uk (212.56.73.32), 30 hops max, 60 byte packets
1  gateway (192.168.0.1)  3.199 ms
2  lo0.11.central11.pcl-bng02.plus.net (195.166.130.152)  11.138 ms
3  irb.11.PCL-CR01.plus.net (84.93.249.97)  10.684 ms
4  cache.akamai.com (212.56.73.32)  11.670 ms[/tt]
With 4.2.2.2, static.bbci.co.uk = 104.86.110.49
[tt]traceroute to 104.86.110.49 (104.86.110.49), 30 hops max, 60 byte packets
1  gateway (192.168.0.1)  1.502 ms
2  lo0.11.central11.pcl-bng02.plus.net (195.166.130.152)  12.116 ms
3  irb.11.PCL-CR02.plus.net (84.93.249.98)  11.958 ms
4  195.99.126.98 (195.99.126.98)  13.577 ms
5  core3-te0-9-0-21.faraday.ukcore.bt.net (109.159.249.165)  13.070 ms
6  peer2-et-3-3-0.faraday.ukcore.bt.net (62.6.201.193)  11.392 ms
7  213.137.183.102 (213.137.183.102)  11.669 ms
8  82.112.115.185 (82.112.115.185)  13.567 ms
9  ae-1.r03.londen05.uk.bb.gin.ntt.net (129.250.6.230)  12.974 ms
10  81.25.207.158 (81.25.207.158)  13.381 ms
11  a104-86-110-49.deploy.static.akamaitechnologies.com (104.86.110.49)  14.954 ms[/tt]
I don't know what the issue is with your computer or connection or elsewhere, there are a couple of other threads currently, but there doesn't seem to be anything widespread or more people would have noticed.

[#13]

Hi ejs,
Thank you for the added info - it have gone completely over my head that the resolutions were not to 'real' google.co.uk, rather a sea of proxy servers / addresses,