If you like to restrict access to a directory on your Apache web server to users from a fixed IP range without password, and the rest of the world with password authentication the httpd.conf section can look like this for Apache-2.2:
<Directory "/var/www/htdocs/protected">
AuthType Basic
AuthName "Protected Area"
AuthUserFile /etc/apache/passwd
Require valid-user
Order deny,allow
Allow from 80.80.80.0/24
Deny from all
Satisfy any
</Directory>
For apache-2.4 the syntax has changed to:
<Directory "/var/www/htdocs/protected">
AuthType Basic
AuthName "Protected Area"
AuthUserFile /etc/apache/passwd
<RequireAny>
Require valid-user
Require ip 80.80.80.0/24
</RequireAny>
</Directory>