This plugin is outdated and might not be supported anymore
JW Forced Login

JW Forced Login

By Jaffe
Details
View on WordPress

If you are not logged into the site it automatically redirects you to the login screen.
All you have to do is activate the plugin to turn it on. Deactivate to turn it off.
After some testing this plugin seems to work fine with multisite

Details

Plugin code:
jw-forced-login
Plugin version:
1.0
Author:
Outdated:
Yes
WP version:
3.0.1 or higher
PHP version:
or higher
Test up to WP version:
3.7.41
Total installations:
10
Last updated:
2013-11-01
Rating:
Times rated:
2
forced-login
redirect