Who's online IP doesn't match server log IP address

More out of curiosity/understanding on my part than a problem.

From where does the Who's Online obtain the displayed IP address, since it doesn't always match server logs.
I occasionally see IP addresses in the
10.x.x.x and 127.0.0.x ranges

Example today is:
Who's online display

127.0.0.1
Session ID: 9dc276d417864f6d4c999711252d1b71
Host: localhost
User Agent: Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; WOW64; Trident/5.0)
/index.php

206.39.41.2
Session ID: 590f23c9fd252b33fa7596cc39f66905
Host: speartip.usar.army.mil
User Agent: Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; WOW64; Trident/5.0)
/index.php

Actual server log for these who's online displays
143.85.76.18
zenid=590f23c9fd252b33fa7596cc39f66905
User Agent: Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; WOW64; Trident/5.0)"