bbPress Forum - rewrite to wwww.mysite prohibits login

I am using bbPress installation without WordPress integration.

The redirect of the RewriteEngine at the forum site works:

RewriteEngine On
RewriteCond %{HTTP_HOST} ^forum.mysite.com$
RewriteRule (.*)$ http://www.forum.mysite.com/$1 [R=301,L]

The problem is the login into ppPress.

bbPress login does not recognize: http://www.forum.mysite/bb-login.php.

It redirects to: http://fo开发者_Go百科rum.mysite.com/bb-login.php.

I tried permalink settings none and name based, same issue.

Does anyone uses redirect in bbPress or how can I eliminate "double" content and redirect permanently to www.?

I redirected from www.forum.mysite.com to forum.mysite.com and achieved to eliminate "double" content.