Autodected Value for dolibarr_main_url_root

Yes I m sorry I wasnt clear enough. Well, First time I installed dolibarr it was accessible by my physhical address which is (172.16.18.20) and now I created a virtual IP for dolibarr in WAF so I want my instance dolibarr to be accessible by the virtual address and what it does now is that once I insert my virtual adress in the browser it tries to redirect me to the physical address in the browser which is not what I want …