DNS issues

[#1]

Hi,
Newbie on here - apologies if this is covered elsewhere and I'm not posting in the right place.
I'm having DNS issues, with some Websites unreachable.  All have been visited previously, including amht.org.uk (OK now, unreachable yesterday) and libreoffice.org
When using Internet Explorer, there's an option to investigate connection problems, and that was where I got the info that there was a DNS issue - normally I use Firefox.
Currently, my Thomson TG585 v8 Router has had the default DNS settings expanded, and reports them:
{admin}=>dns server route list
DNS Server Entries:
DNS Server    Source                Label        Metric Intf        State  Domain
S                  212.159.13.49            1              Internet            UP        *
S                  212.159.13.50            2              Internet            UP        *
S                  208.67.220.220          4              Internet          UP          *
S                  208.67.220.222          5              Internet          UP          *
D                    212.159.6.9            10            Internet          UP          *
D                    212.159.6.10          10            Internet          UP          *
Any suggestions?

[#2]

Hi there.
There's no issues that we're aware of at present.
I've been able to look up both websites using our DNS servers without any issues.
Are you still having issues?

[#3]

OK now, but I'm going to be watching things carefully!

[#4]

I'm not sure what happens with the above having 6 dns ip's in the routers forward table.
In the standard situation with the two plusnet IP's both with a metric of 10. The PC sends a name lookup to the router on 192.168.1.254, the router then forwards the lookup to both plusnet IP addresses.
Eventually the reply arrives from one of PN's servers and is passed on to the PC, when the slower server answers that reply is also passed to the PC.
With the above setting the PC will send the lookup to 192.168.1.254, but does the router then:
a) forward the query to each metric in turn waiting each time until the previous metric has failed to give a answer.
b) only forward to the metric 1 server.
c) send the query to all metrics at the same time.
I'm guessing a) but it's only a guess, anyone have a definitive answer?

[#5]

Quote from: npr

I'm not sure what happens with the above having 6 dns ip's in the routers forward table.

... and four of the six go to the same physical boxes!

[#6]

Quote from: npr

In the standard situation with the two plusnet IP's both with a metric of 10. The PC sends a name lookup to the router on 192.168.1.254, the router then forwards the lookup to both plusnet IP addresses. Eventually the reply arrives from one of PN's servers and is passed on to the PC, when the slower server answers that reply is also passed to the PC.

Are you sure the computer receives two DNS reply packets from the router if the query is sent to both and both reply? I assumed the later reply received by the router would just be discarded.
Edit: found the post with a log from the router DNS forwarder with tracing enabled.

[#7]

Interestingly, I've been running the GRC DNS Benchmark and of the 50 "fastest" servers, the "four" Plusnet entries are in the six that "lose" requests
I was looking to see if I could optimise DNS operations 

[#8]

Quote from: PeeGee

I was looking to see if I could optimise DNS operations

My preference for a single windows machine is to use "Acrylic dns proxy" primed with the 4 fastest resolvers found with dns benchmark.
http://mayakron.altervista.org/wikibase/show.php?id=AcrylicHome

[#9]

The Plusnet DNSes have 'lost' lookups like that for as long as I can remember. 
Here is a benchmark that I ran three days ago -

[#10]

I have no issue with Plusnet Dns Servers at all, slower than other options maybe!, failures,,, No.

[#11]

Quote from: npr

My preference for a single windows machine is to use "Acrylic dns proxy" primed with the 4 fastest resolvers found with dns benchmark.

Aaaah! insufficient information provided
I run a Mint17 system which provides DNS and DHCP, so the router items are "off", with DHCP setting "plusnet" as the "backup" for DNS. It was the forwarding aspect I was looking at, currently using openDNS.
I mostly run MS Windows in VBox, when I do run it, though I do have a dual-boot laptop as well
Phil