http response uri rewrite based on server IP

Well, NEW server has to authenticate users, but database is not moved from OLD server yet. Programmers will move one user by one from OLD server to NEW but meanwhile all connection to www.host.com must be forwarded to NEW server (F5 match host and sends to pool “NEW server” ), if server cannot find right user in its database then NEW server responds to user with redirect to www.host.com/a1, and this requests on F5 is matched by URI “/a1” and sent to pool “OLD server “ where user database is full and then users are working with OLD server.

 

Old server URL are the same as on NEW server, and I am inserting this “/a1” only in communication between user and F5 and purpose is to indicate if connection should be sent to NEW or OLD server. I believe that if user will click on some links inside OLD server the requests by F5 will be sent to NEW server because there will be no “/a1” in link and F5 will not match this URI . I need to ensure that redirected user to OLD server will always stick to this server until the end of session. This is why I think I need to insert “/a1” for all responses that are coming from specific IP – OLD server IP.

 

Yes, it sound confusing … But I got this task to do and I really need advice how to implement this on F5 using irules.