I was given 6 Public IP's by my ISP,Presently I have used up 5 of them.But would like to free up 2.My modem is connected to a router,which is in turn connected to a ASA firewall,to a Switch and to a Mikrotic Hotspot.How can I achieve this? Or do I clear the NAT?
What you use 5 addresses for to start with?
I mean, seriously. You setup sounds like you need ONE - with a router supporting NAT, and all the rest is behind that.
I see nothing in your explanation requiring the use of more than one IP address publicly - just use NAT to hide your network behind one address.
As others have mentioned, you may be able to free up some of your addresses simply by reviewing what they are used for and confirming that they require a public address.
Beyond that, I would investigate using Port Address Translation (PAT) to make better use of the address space. This will allow you to use one public IP address for multiple services i.e. your web, mail and ftp servers could all be NAT/PAT'd behind one IP address.