tesagig

thank you! assuming there is no additional security risk?

I tried this. But IP is kept. I did some research on this and clients typically don't give up IP like this. Actually, some people have to go though great lengths to change IP (i.e. switch to static and then switch back) . In any case I woudl not expect to get the error after upgrading USG firmware.

clients kept IP and DHCP server (on USG) is not giving out new IP to client or is not recording existing IP-MAC binding on the network.

Seems like the clients want to check for existing MAC-IP binding, and USG is rejecting because it forgot but does not force a new IP?

Yes, I did configure IP/MAC binding.At least some clients were unable to obtain IP address. Only after reboot.

thanks. I know there lots of ports ranges. I was hoping that Zyxel had a predefined rule. BTW. What are applications used for?