Jeremy Pry

Force all of the users on your Multisite Network to login at the main site address.

Redirect Network Login

Redirect the the wp-login.php for sub-sites to the main site

voceplatforms

smccafferty

Single sign on for a multisite WordPress implementation. Users are authenticated for all sites across the network. 
This plugin is best used within a domain mapped environment where the normal domain authentication cookie would not apply. 
Uses internal WordPress authentication functions, including maintaining the use of the standard WordPress login page, 
to authenticate the user across the network.
Settings to customize the SSO login/logout loading page by inheriting the default WordPress login page CSS, custom login page CSS included in theme or even specifying CSS.
IMPORTANT: In order for this plugin to work properly, it MUST BE network enabled. The web server also needs to support JSONP requests.
Please refer to full documentation at https://github.com/voceconnect/wp-multisite-sso/wiki.

WP Multisite SSO

Single sign on for a multisite WordPress implementation. Users are authenticated for all sites across the network.

Redirect Network Login vs WP Multisite SSO