Hello,
I have tried with "streams" as you advised me. It solves 50% of my problem. There are two java scripts to upload files to the WEB. First java script sends an HTTP request to the client that includes real servers hostsnames configuration for the JS in the header; your irule works fine. Second java script does not send any information into the HTTP header; your irule didnt work. I changed a variable in each apache server behind the BigIP:
HTTPD_SERVERNAME=real_name.domain.com
to
HTTPD_SERVERNAME=virtual_server_name.domain.com
and now java scripts do not modify client URL. Any jump to the real_name.domain.com ends in virtual_server_name.domain.com. Fortuantely it has not been necessary to modify any javascript.
I am grateful for your help (cmbhatt and Aaron)
Best regards