Dynamics NAV 2017 (2018 and 2016 too) creates a default web client access , with de default server configuration authenticaton ( Windows in my case), to change web client to use NavUserPassword ,is a easy task:

create a second service :

You need to create a selfsigned certificate or add your legacy certificate, an extra configuration is necessary:


then you only have to modify web.config file in the webclient directory:

you have to modify servicename, port , ClientCervicesCredentialType, and DnsIdentity:


Enable forms auth on the iis ,and disable windows auth:

for more information check this fantastic post: