Irule for url redirection

I think the best (most efficient) way to do this would be by using an LTM Policy to do the redirect. The following SOL document lists the steps to create a profile that will redirect HTTP requests to HTTPS, so you could just change some of the details to fit your requirements. https://support.f5.com/kb/en-us/solutions/public/14000/900/sol14996.html

Basically, in the condition, you would check

http-host equals abc.mydomain.com

http-uri equals /

http-reply redirect location http://abc.mydomain.com:8080/update/manifest/Login.jsp