Netgear M5300-28G (GSM7228S) - ProSAFE 24-port Gigabit L2+ Managed Stackable Switch Administrator's Guide

Select Security > Control > Captive Portal > CP Configuration. 

A screen similar to the following displays.

Under Captive Portal Configuration, scroll down and select the CP 1 check box. Now CP 1 
appears in the CP ID field at the top.

In the Block field, select Enable.

Click Apply to save the settings.

When using local authentication, the administrator provides user identities for captive portal 
by adding unique user names and passwords to the local user database. This configuration is 
global to the captive portal component and can contain up to 128 user entries (a RADIUS 
server should be used if more users are required). A local user can belong to one or more 
groups. There is one group created by default with the group name Default to which all new 
users are assigned. All new captive portal instances are also assigned to the Default group. 
You can create new groups and modify the user/group association to allow only a subset of 
users access to a specific captive portal instance. Network access is granted upon 
successful user name, password, and group verification.

Create a group whose group ID is 2.

(Netgear Switch) #config

(Netgear Switch) (config)#captive-portal

(Netgear Switch)(Config-CP)# user group 2

Create a user whose name is user1.

(Netgear Switch) (Config-CP)#user 2 name user1