IP of some log entries are shown as two colons


some entries of my visitor log do not show the IP-address of the visitors but two colons instead (see the second entry in the following screenshot):

Is there a problem with translating the IP-addresses into hexadecimal system? Or does it have to do with IPv6? Everything else seems to be working ok, so it is not really a problem. I think these double colons started first, when I upgraded my ubuntu to 16.04 (and with it the php from 5.something to 7).

All information about this would be very helpful.


The problem is solved. There was a server misconfiguration after upgrading the webserver OS to the latest version.