Here is the way you set up login banner for WLC. First of all you have to create your banner in notepad and save it as a .txt file. Then you have to download this onto WLC using a TFTP server. You can use WCS (as it has TFTP server running on it) or you can use a different TFTP server as well. I have created a txt file called “WLC-banner.txt” for this.

Then you have to go “Commands > Download File” section & select File Type as “Login Banner” & transfer mode as “TFTP”. Fill the rest of detail as required & then initiate the download.

You can do the same via CLI as well. Here is the config commands to download this banner onto WLC via CLI.

(WLC1) >transfer download datatype login-banner
(WLC1) >transfer download mode tftp 
(WLC1) >transfer download filename WLC-banner.txt
(WLC1) >transfer download serverip 192.168.1.9
(WLC1) >transfer download path .
(WLC1) >transfer download start 

Mode............................................. TFTP  
Data Type........................................ Login Banner
TFTP Server IP................................... 192.168.1.9
TFTP Packet Timeout.............................. 6
TFTP Max Retries................................. 10
TFTP Path........................................ ./
TFTP Filename.................................... WLC-banner.txt

This may take some time.
Are you sure you want to start? (y/N) y
TFTP Login Banner transfer starting.
TFTP receive complete... checking login banner.
Successfully installed new login banner file.

Once download process is complete you can verify this by log out & login to the controller (either CLI or GUI). Here is my login screen afterwords.

Here you will see it once log in via CLI

***** Hey Rasika !!! You have less than 90 days left... 
Study hard to become a CCIE Wireless *****
(WLC1) 
User: admin
Password:***********
(WLC1) >

You can clear the login banner via “Commands > Login Banner > Clear” as shown in the below.

In CLI, you can use “clear login-banner” command to do this.