Disable IPv6 on Loopback address (Localhost, Computer name, …)

ipv6loopbackwindows-server-2008-r2

We tried installing a 3rd party software product on a new Windows Server 2008 R2 machine and found that everything works except for accessing local services through loopback addresses such as localhost or the computer name (ex: VPS-Web which resolves to localhost). We are not using IPv6 and would like to disable it until the software is compatible.

I tried using these instructions for disabling IPv6 on Windows 2008 R2 but it did not disable the protocol for localhost. Pinging localhost or VPS-Web will still return ::1: instead of 127.0.0.1. I can use ping localhost -4 to get the correct address, but IPv6 takes precedence over IPv4 so the 3rd party software only gets the IPv6 address.

Best Answer

I had initially checked the host file as SilverbackNet suggested, but on a Windows 2008 R2 server this is the default file:

# localhost name resolution is handled within DNS itself.
#   127.0.0.1       localhost
#   ::1             localhost

# indicates a comment in the host file, so all the entries are commented out, and the first line is a bit confusing. I then noticed that there were two entries for localhost that were commented out, so I tried uncommenting the IPv4 one and it worked! I should have tried that first but I was thrown off track by the first line. Using the below host file pinging the computer name or localhost will always return an IPv4 address, which fixes the problem with the 3rd party software! 

# localhost name resolution is handled within DNS itself.
#   ::1         localhost
127.0.0.1       localhost
127.0.0.1       VPS-Web
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