I know. But cant control many pos or devices power down directly. How db pool release active ip. I use rlm tool In the crontab every 30 minutes. But I think wrong way. Can you give for active session on the db ippool time out value or any way?

Or different configuration.

Note: this devices is POS. On the gprs network. I have lease line gsm provider and my client is gsm NAS server.

No, there is no lease duration in ippool. Perhaps you should consider DHCP. Ivan Kalik