One day a person stayed in a hotel and plugged an Ether cable to the information socket in his room. But Windows could not gain access to any web pages. He asked the hotel and the hotel staff told him, type ipv6 uninstall. After this operation, the Windows came to be on the net. (This is probably because of a poor implemented hotel system.)
Mozilla on Linux 2.4 takes a few seconds to gain access to web page which is provided with IPv4 but registered with IPv6 as well as IPv4. (This is due to a harmful specification called “on-link assumption”.)