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TP-Link websites & P/N DNS Servers

buseng12
Grafter
Posts: 368
Registered: 14-06-2013

TP-Link websites & P/N DNS Servers

I noticed that I couldn't access several TP-Link (router etc manufactures) websites including the UK one. The US one worked.
After a bit of fiddling it seems Plusnet's default DNS servers are the problem. I set my ethernet adaptor to use Google DNS & I can now access all the TP-Link sites ok including the UK one.
Is there any reason why Plusnet's  DNS servers are blocking these sites?
24 REPLIES
Community Veteran
Posts: 5,155
Thanks: 474
Fixes: 19
Registered: 10-06-2010

Re: TP-Link websites & P/N DNS Servers

I saw it was broken for a moment yesterday, but after running dig a few times it started working normally again.
I think it's the DNS servers for tp-link.com (ns15.xincache.com and ns16.xincache.com) that are down or having problems, or connectivity to or from those to plusnet - while I was typing this, they worked again for a moment.
Nothing is being deliberately blocked, it's just that other DNS servers may cache positive responses for longer.
Community Veteran
Posts: 1,841
Thanks: 103
Fixes: 6
Registered: 21-01-2013

Re: TP-Link websites & P/N DNS Servers

Can you please post the TP-Link URL's you're having the problem with.
The only UK URL I've found is uk.tp-link.com, it resolves ok here with PN's dns.
buseng12
Grafter
Posts: 368
Registered: 14-06-2013

Re: TP-Link websites & P/N DNS Servers

That is the one amongst others. If I set my ethernet adaptor to "obtain DNS servers automatically"  it wouldn't work, however when  I put Google ones in  it was ok.
Strange the US site worked ok.
adie:quote
Community Veteran
Posts: 1,841
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Registered: 21-01-2013

Re: TP-Link websites & P/N DNS Servers

My mistake, must have been in my cache.
Here dig does not resolve uk.tp-link.com using Plusnet resolvers.
Resolves ok using opendns, google dns, level3 dns and the root servers.
Looks like a PN issue from here.
buseng12
Grafter
Posts: 368
Registered: 14-06-2013

Re: TP-Link websites & P/N DNS Servers

Confirmed, switched back to P/N's DNS servers & again nothing. Both Chrome & IE cannot open the pages.
Wonder if the P/N team will pick this up tomorrow.
Community Veteran
Posts: 5,155
Thanks: 474
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Registered: 10-06-2010

Re: TP-Link websites & P/N DNS Servers

At the moment, for me at least, Plusnet DNS are resolving uk.tp-link.com and tp-link.com, but dig +trace will get as far as finding ns15.xincache.com and ns16.xincache.com as the nameservers for the tp-link.com domain, but these often timeout.
Trouble is, if you repeat the same query 20 or so times in quick secession, even Plusnet's DNS servers will manage to remember the answer for a little while.
Community Veteran
Posts: 1,841
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Registered: 21-01-2013

Re: TP-Link websites & P/N DNS Servers

Still much the same this morning, plusnet's dns can not resolve uk.tp-link.com whereas other resolvers can.
There's been sufficient time for it to expire from the various dns caches so it's not being served from a old google dns cache entry.
Dig +trace is still being intermittent in finding the name, so perhaps there's a plusnet routing issue to xincache.net.
Quote
; <<>> DiG 9.8.6-P1 <<>> uk.tp-link.com +trace
;; global options: +cmd
.                      441028  IN      NS      a.root-servers.net.
.                      441028  IN      NS      b.root-servers.net.
.                      441028  IN      NS      c.root-servers.net.
.                      441028  IN      NS      d.root-servers.net.
.                      441028  IN      NS      e.root-servers.net.
.                      441028  IN      NS      f.root-servers.net.
.                      441028  IN      NS      g.root-servers.net.
.                      441028  IN      NS      h.root-servers.net.
.                      441028  IN      NS      i.root-servers.net.
.                      441028  IN      NS      j.root-servers.net.
.                      441028  IN      NS      k.root-servers.net.
.                      441028  IN      NS      l.root-servers.net.
.                      441028  IN      NS      m.root-servers.net.
;; Received 508 bytes from 192.168.1.10#53(192.168.1.10) in 15 ms
com.                    172800  IN      NS      a.gtld-servers.net.
com.                    172800  IN      NS      b.gtld-servers.net.
com.                    172800  IN      NS      c.gtld-servers.net.
com.                    172800  IN      NS      d.gtld-servers.net.
com.                    172800  IN      NS      e.gtld-servers.net.
com.                    172800  IN      NS      f.gtld-servers.net.
com.                    172800  IN      NS      g.gtld-servers.net.
com.                    172800  IN      NS      h.gtld-servers.net.
com.                    172800  IN      NS      i.gtld-servers.net.
com.                    172800  IN      NS      j.gtld-servers.net.
com.                    172800  IN      NS      k.gtld-servers.net.
com.                    172800  IN      NS      l.gtld-servers.net.
com.                    172800  IN      NS      m.gtld-servers.net.
;; Received 492 bytes from 199.7.83.42#53(l.root-servers.net) in 46 ms
tp-link.com.            172800  IN      NS      ns15.xincache.com.
tp-link.com.            172800  IN      NS      ns16.xincache.com.
;; Received 111 bytes from 192.12.94.30#53(e.gtld-servers.net) in 76 ms
;; connection timed out; no servers could be reached


Community Veteran
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Registered: 29-06-2010

Re: TP-Link websites & P/N DNS Servers

12½ hours later - still not working.
Community Veteran
Posts: 5,155
Thanks: 474
Fixes: 19
Registered: 10-06-2010

Re: TP-Link websites & P/N DNS Servers

It should be an intermittent problem, but I suspect part of the problem is that Plusnet DNS servers are storing the negative answer for a while, and not retrying the query often enough.

; <<>> DiG 9.9.4-P2-RedHat-9.9.4-12.P2.fc20 <<>> @212.159.13.49 uk.tp-link.com +tries=1
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 64
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;uk.tp-link.com. IN A
;; ANSWER SECTION:
uk.tp-link.com. 2695 IN A 91.250.77.30
;; Query time: 23 msec
;; SERVER: 212.159.13.49#53(212.159.13.49)
;; WHEN: Tue Jul 08 06:03:57 BST 2014
;; MSG SIZE  rcvd: 59

After many repeated queries, 212.159.13.49 now knows the IP address.
; <<>> DiG 9.9.4-P2-RedHat-9.9.4-12.P2.fc20 <<>> @212.159.13.50 uk.tp-link.com +tries=1
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: SERVFAIL, id: 45766
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 1
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;uk.tp-link.com. IN A
;; Query time: 22 msec
;; SERVER: 212.159.13.50#53(212.159.13.50)
;; WHEN: Tue Jul 08 06:05:27 BST 2014
;; MSG SIZE  rcvd: 43

However 212.159.13.50 was not so lucky and never managed to get the IP address, and now just serves up SERVFAIL in 22ms - it can't possibly have tried ns15.xincache.com or ns16.xincache.com in less than 22ms.
I also just saw occasional SERVFAIL replies from 4.2.2.1 and 208.67.220.220 for uk.tp-link.com - but it seems these servers don't stick with the SERVFAIL answer for so long - retry a couple of times and they'll return the IP address.
Community Veteran
Posts: 5,155
Thanks: 474
Fixes: 19
Registered: 10-06-2010

Re: TP-Link websites & P/N DNS Servers

Either it was just a coincidence, or the PCL plusnet DNS servers were much better at resolving tp-link.com domains to IP addresses than the PTN DNS servers.
Community Veteran
Posts: 1,841
Thanks: 103
Fixes: 6
Registered: 21-01-2013

Re: TP-Link websites & P/N DNS Servers

Quote
; <<>> DiG 9.8.6-P1 <<>> @212.159.13.49 uk.tp-link.com
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 6684
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0
;; QUESTION SECTION:
;uk.tp-link.com.                        IN      A
;; ANSWER SECTION:
uk.tp-link.com.        1619    IN      A      91.250.77.30
;; Query time: 31 msec
;; SERVER: 212.159.13.49#53(212.159.13.49)
;; WHEN: Fri Jul 11 18:46:46 GMT Summer Time 2014
;; MSG SIZE  rcvd: 48

Quote
; <<>> DiG 9.8.6-P1 <<>> @212.159.13.50 uk.tp-link.com
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: SERVFAIL, id: 26850
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 0
;; QUESTION SECTION:
;uk.tp-link.com.                        IN      A
;; Query time: 31 msec
;; SERVER: 212.159.13.50#53(212.159.13.50)
;; WHEN: Fri Jul 11 18:47:16 GMT Summer Time 2014
;; MSG SIZE  rcvd: 32

The problem is still there.
Plusnets response is deafening.  Undecided
Gateway: ptw-ag01

Community Veteran
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Registered: 10-06-2010

Re: TP-Link websites & P/N DNS Servers

The different DNS server IP addresses don't matter - if you're on a PCL gateway, 212.159.6.9, 212.159.6.10, 212.159.13.49 and 212.159.13.50 go to PCL DNS servers, if you're on PTN / PTW gateways, the same 4 IP addresses go to PTN DNS servers. The DNS servers no longer respond on the other IP addresses so you can't test the PTN dns servers if you're on a PCL gateway and vice versa.
Earlier this evening I was on pcl-ag06 and the PCL plusnet DNS servers were resolving tp-link.com domains, but shortly later my line dropped and I'm now on ptn-ag02, and the PTN DNS servers tend to return the SERVFAIL responses. At the time this thread started, I was on ptw-ag04.
Community Veteran
Posts: 5,155
Thanks: 474
Fixes: 19
Registered: 10-06-2010

Re: TP-Link websites & P/N DNS Servers

It was very likely just a coincidence, I'm back on pcl-ag06 and the plusnet DNS servers aren't working any better.
Community Gaffer
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Re: TP-Link websites & P/N DNS Servers

Quote from: ejs
I think it's the DNS servers for tp-link.com (ns15.xincache.com and ns16.xincache.com) that are down or having problems...

I'd be inclined to agree. Their auth servers take an awfully long time to reply:
~$ dig tp-link.com @ns15.xincache.com
; <<>> DiG 9.3.4-P1.2 <<>> tp-link.com @ns15.xincache.com
; (1 server found)
;; global options:  printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 33291
;; flags: qr aa rd; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0
;; QUESTION SECTION:
;tp-link.com.                  IN      A
;; ANSWER SECTION:
tp-link.com.            3600    IN      A      50.62.149.47
;; Query time: 533 msec
;; SERVER: 125.78.242.30#53(125.78.242.30)
;; WHEN: Tue Jul 15 11:37:32 2014
;; MSG SIZE  rcvd: 45

And often do this:
~$ dig tp-link.com @ns15.xincache.com
; <<>> DiG 9.3.4-P1.2 <<>> tp-link.com @ns15.xincache.com
; (1 server found)
;; global options:  printcmd
;; connection timed out; no servers could be reached

The TTL on the domain is an hour so in the event of a successful lookup, things will appear OK for a while. It's hit and miss whether or not you get a reply though. AIUI, if there's no reply, we'll fail the domain for 15 minutes.
We did have an internal problem raised to look into this (ref: 82031) however it was determined that whatever was causing the issue was outside of our network.

Bob Pullen
Plusnet Product Team
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