Rahman,
I don't think you can ping the 10.100.60.2 address because your clients are not authenticated. On my client report, there is a "green lock" denoting authentication. (Similar to the Apple device on eduroam with the 172.x.xx. address) On your list, I see the clients have a grey "unlocked" icon.
Can you disable authentication temporarily to test?
For an Internal Captive Portal deployment, you will want a Non-Auth Role (similar to the screen shot below, referenced in the knowledgebase link in my original post)
Regards,
Jason