"We have to add a host file to the sharepoint server" -
Do you mean you are putting the DNS name of the sharepoint server into the host file on the client which is accessing the loadbalancer?
If so - there are non-relative links or redirects occuring.
If its a redirect, ACE can rewrite the Location header if its HTTP between the ACE and the server.
Can you share your config on your ACE?
-Chris