Users matching a soft ban (also called: soft kline or soft gline) are only be allowed in if they authenticate with services.
Placing a soft ban
On IRC you prefix the KLINE or GLINE with a percent sign:
/KLINE %*@192.168.* 0 Please authenticate.
In spamfilter and in the configuration file several soft actions are available.
Effect on the user
Assuming you have the optional module authprompt loaded the user will see this:
[11:56:08] -server.test.net- The server requires clients from this IP address to authenticate with a registered nickname and password. [11:56:08] -server.test.net- Please reconnect using SASL, or authenticate now by typing: /AUTH nick:password [11:56:08] -server.test.net- If you don't have a registered account then go to https://example.org/
The user can then configure SASL in their IRC client, or they can simply type
Only after successful authentication the user will be fully online. So before authentication the user cannot join channels, message users, etc.
For more information on forcing authentication and conditional banning, see the Authentication article.