Add a rewrite rule for HTTP to the file:
RewriteEngine on
RewriteRule ^/$ http://<host_name>/<feature> [R,L]
Where <host_name> is the URL that users will access, and <feature> is the context path of the default feature, including Activities, Blogs, Communities, Dogear, Home page, or Profiles. For example:
RewriteEngine on
RewriteRule ^/$ http://connections.acme.com/homepage [R,L]