Thanks gents.. I believe my rule appears to be doing what its suppose to, which is rewriting the host header, I've confirmed that using the logging function, thanks for the help there.
I think my problem is happening during the sign in process where the referring URL is getting lost. For those users that want to log in and make changes to the site via the content management interface they access a secure page first to login. With out the rule in place the Request Header reads: GET /CMS/Login.aspx?referrerUrl=http%3a%2f%2fcms.test.sitename.us.comv%2fg2p%2fK.... With the rule in place the Request Header reads: GET /CMS/Login.aspx?referrerUrl=http%3a%2f%2fsitename.us.com%2fg2p%2fK... Which is the reason why I’m being directed back to my production read only version of the site and not the test content management interface area of the site.
So the host header getting rewritten at the LTM level is messing with the referring URL, I'm not sure there is a way around this one..
Bob