301 redirects for subdomains on Multisite?

I change the URL of subdomain of a blog to a new subdomain, then when you type the old url address you will be redirect to a new blog sign up page. How to 301 redirect it to the new subdomain instead of the sign up page?
I have tried this rewrite rules but not work.
RewriteRule ^winrar-download.softadm.com$ http://winrar.softadm.com/ [R=301,NC,L]