Programmatically Changing NameServer in Windows TCP/IP

Question

Hello, I am building a VPN application where I need to set DNS server programmatically. I am changing NameServer parameter in the registry (in HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\Interfaces) to prepend a name server to the list of existing entries. Once I do this, if I try to look up a host name using nslookup, it works fine, but ping is not able to resolve the name - for 15 minutes. And after 15 mins ping is also able to resolve the name. I've tried my own little TCP/IP app, and that has the same issue. I looked at the traffic in wireshark, and I see that nslookup is sending dns lookup requests, while ping isn't.

Is there anyway I can kick windows to notice the name server earlier? Or is there a better way to set name servers in windows?

Thanks in advance for your help!

Answer 1

Don't change that registry key directly. As you've found, it doesn't notify DNS clients that the nameserver has changed.

The easiest solution is probably %SystemRoot%\system32\netsh.exe.

netsh interface ip set dns name="Local Area Connection" source=static addr=...