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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?

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Please explain in detail what these 5 IP addresses are used for. A small diagram showing your setup would also help. – wolfgangsz Aug 6 '10 at 8:22

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.

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In addition to that, why the need to free up 2 addresses? – John Gardeniers Aug 6 '10 at 10:57
I don't find it so hard to believe that he needs another ip address. I have 6 ip addresses from my ISP and I'm using 5 of them as well. 1 for general NAT on the firewall, 1 for our phone system which requires one-to-one NAT, and 1 each for 3 terminal servers. – joeqwerty Aug 6 '10 at 11:34
Well, that is wasting like hell (I use ONE myself for NAT, Phone AND terminal servers). But even then, the poster does not say he has a phone system or multiple terminal servers, which makes it unlikely he really needs them. – TomTom Aug 6 '10 at 17:51
D old System Administrator configured it in such a way dat,1 is for the modem,1 for Exchange,I for the general NAT on the router n 2 for d NAT pool.Are the 3 expended on the router really important.Can't I reconfigure n use 1.And how do I do dis? – Lawdricky Aug 9 '10 at 14:10
1 for the modem? Makes no sense. NAT pool makes no sense either (unless there is a special reason which you do not say there is). Exchange also does not need it's own. I run a complete company using 1 external NAT (+ servers, but they are totally separate) thanks to using a firewall, not ONLY a SIMPLE NAT. – TomTom Aug 9 '10 at 14:30

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.

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