IPv6 is an integral part of Windows. It's tempting to disable IPv6 on Windows 10 especially on home networks. This can have a variety of side effects that might cause applications and processes to misbehave. Microsoft explicitly does not recommend you disable IPv6. The best way to ensure your Windows 10 computer uses IPv4 is to simply change the IPv6 prefix policy precedence. To do this open an elevated command prompt and type:

netsh interface ipv6 show prefixpolicies

You should see the following output:

Precedence  Label  Prefix
----------  -----  --------------------------------
        50      0  ::1/128
        40      1  ::/0
        35      4  ::ffff:0:0/96
        30      2  2002::/16
         5      5  2001::/32
         3     13  fc00::/7
         1     11  fec0::/10
         1     12  3ffe::/16
         1      3  ::/96

The first line with a precedence of 50 is the IPv6 loopback adapter. The second line with a precedence of 40 is the IPv6 default gateway. The third with a precedence of 35 is all IPv4 compatible addresses. To change the precedence, type the following:

netsh interface ipv6 set prefixpolicy ::ffff:0:0/96 46 4

The value 46 is the new precedence. Windows uses this value order prefix lists based on destination. The lower the value, the less preferred that destination is. The value of 4 is the label. Windows uses this value to order the source preference based on the destination prefix. Then type:

netsh interface ipv6 show prefixpolicies

You will now see the priority has changed as follows:

Precedence  Label  Prefix
----------  -----  --------------------------------
        50      0  ::1/128
        46      4  ::ffff:0:0/96
        40      1  ::/0
        30      2  2002::/16
         5      5  2001::/32
         3     13  fc00::/7
         1     11  fec0::/10
         1     12  3ffe::/16
         1      3  ::/96

Now when you complete (for example), a DNS lookup, the IPv4 DNS server address will be used in preference to the IPv6 address. For example:

C:\>nslookup
Default Server:  dns.zone.firedaemon.int
Address:  192.168.0.7

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