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I have been able to work around my issue, so I am not looking for a solution, but I am looking for an answer as to why I am seeing the behaviour as described here:

Context: I'm developing an application that uses a software component to relay email messages out, using a local SMTP server component. I'm on a Windows 7 dev machine on a residential broadband connection behind a Virgin Media Super Hub router.

The component requires that I specify a DNS address for domain name resolution. Initially, I used the DNS server address as specified in my TCP/IPv4 connection properties. My attempts to relay email failed with a time out at domain name resolution.

enter image description here

I used cmd window "nslookup". This failed with a time out:

enter image description here

So I used "ipconfig/all" to check name servers again. The name server is reported as being at address

enter image description here

At this point my internet connection is working as normal, so I change my TCP/IPv4 connection properties to "Obtain an IP address automatically" and "Obtain an DNS server address automatically".

Following this, I test SMTP relay, and it works.

I use "ipconfig/all" again, and find that my name servers are now reported as:

Now I change my TCP/IPv4 connection properties back to the fixed settings as before.

Providing that I continue to specify as the name servers in my SMTP relaying application, everything works, despite Windows being configured to use

I don't like not understanding why:

  1. I'm unable to check the DNS server that is in use using standard cmd methods.
  2. Why windows appears to be using a different DNS server address to that which is configured.

Could anyone address the above points, and also answer my question here:

  1. Is it possible that my router is translating DNS addresses for some types of query, but not for others?

Any light that can be shed here is appreciated!

share|improve this question
the answer to question 1 is the standard tools were working just fine and were reporting acurately and 2 it was not using different dns server to return results it was just using misconfigured dns settings . The only case were this is not true is if you have either a virus or you modified you hosts file. – tony roth Jun 3 '13 at 13:18
This looks like a problem with your home network router. Oh, and consider using software components which don't suck. Your application will be better. :) – Michael Hampton Jun 3 '13 at 16:22
Given that nslookup also failed, I won't be blaming the software components on this occasion. – gb2d Jun 3 '13 at 20:39
up vote 4 down vote accepted

It looks like you're encountering an odd quirk with their DNS setup. and appear to be ISP DNS servers. is an OpenDNS server, and is your router's DNS (which is probably using one of the former for DNS resolution).

So, I'm concluding that your router's DNS is either non-existent or not functioning properly. However ...when you're using DHCP, your "automatic" settings switch to ISP-assigned settings rather than the router settings. So...probably just a quirk on how the network it set up.

share|improve this answer
Seems to be the consensus. Good to hear that it's most likely a fault and not another massive gap in my networking knowledge! – gb2d Jun 3 '13 at 20:40

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