Apple Computers Not Connecting to the Internet
From my understanding, if you have both IPv4 and IPv6 connectivity, the Mac operating system will try both and determine which is fastest. The problem is if the IPv6 DNS returns an IPv6 address that can not be reached, then the computer waits until it times out. This happens even it the IPv4 network reaches the web site. The only reasonable solution is to configure IPv6 as Link-local only.


Under System Preferences select Network.
Select the type of connection. (Ethernet, Wi-Fi, etc.)
Select Advanced...
Select the TCP/IP tab.
Select Link-local only as shown below.
Click on OK.
Click on Apply.




Link-local only means the IPv6 addressing will work for your Local Area Network (LAN), but is disabled on the Wide Area Network (WAN).

BTW, Microsoft has a fix for this, but only for Windows users. Download "Perfer IPv4 over IPv6 in prefix policies" from this site. There is way to make a similar change to the prefix policies used by the underlying Unix on a Mac. Unfortunately, from my understanding, OS X will ignore the change.