Authenticate http requests EXCEPT for from this IP
"satisfy any" is indeed what you need to use. There is a good example on the Apache wiki. To quote directly from that source:
<Directory /home/www/site1/private>
AuthUserFile /home/www/site1-passwd
AuthType Basic
AuthName MySite
Require valid-user
Order allow,deny
Allow from 172.17.10
Satisfy any
</Directory>