Source:
https://asusrouterssetups.com/2019/12/17/how-setup-login-asus-ac-1900-wifi-routerrouter-asus-com/
You can easily access the guest network in the Asus AC1900router. First, you enter all details in the web browser. After this, you can go to the advanced settings of the router. Now you can go to the left side of the settings. Now you can enable the guest network and use it to access the network of the guests. If you need any help click on https://asusrouterssetups.com/2019/12/17/how-setup-login-asus-ac-1900-wifi-routerrouter-asus-com/