Router – DNS server in use is not that as specified in TCP/IPv4 properties. Why? [Windows 7]

domain-name-systemrouterwindows 7

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.

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

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So I used "ipconfig/all" to check name servers again. The name server is reported as being at address 192.168.0.1

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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:

194.168.4.100
194.168.8.100

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

Providing that I continue to specify 194.168.4.100 as the name servers in my SMTP relaying application, everything works, despite Windows being configured to use 192.168.0.1.

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!

Best Answer

It looks like you're encountering an odd quirk with their DNS setup.

194.168.4.100 and 194.168.8.100 appear to be ISP DNS servers. 208.67.222.222 is an OpenDNS server, and 192.168.0.1 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.

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