help with Irule to change url from servername

Please allow me to clear up one more detail. The Redirect Rewrite option in the HTTP profile is NOT used to rewrite URLs. This option, when applied to an HTTPS (SSL) virtual server, will rewrite any redirects, actual 30x type messages, from the server if they contain "http://" instead of "https://".

The challenge in your request is dependent on where and how often this internal URL shows up. If it's simply in a redirect, and/or that Host header needs to be presented to the server to prevent it from redirecting, then that's pretty easy to solve with a quick iRule. If, however, that URL is wrapped around object reference, images, JavaScript, style sheets, then you'll most likely need either a more complex iRule, the ProxyPass iRule, or the rewrite profile in 11.4.