So since you need only webserver authentication, you dont need to configure anything in weblogic. Even LDAP is not necessary in weblogic side.
1. You have setup basic AUTH in webserver for some URL of weblogic.
2. Webserver plugin talks to weblogic
3. When you request a page in weblogic, it goes via webserver and it should throw BASIC AUTH page.
4. Once you authenticate, the requests goes to weblogic.
Turn off any LDAP integration you have done in weblogic or any other security setting.