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New Member

NAT versus PAT

I am looking for a really good explanation and sample of PAT and NAT. It seems that the two acronyms are interchanged fairly often.

2 ACCEPTED SOLUTIONS

Accepted Solutions
Silver

Re: NAT versus PAT

http://www.cisco.com/en/US/customer/products/hw/vpndevc/ps2030/products_tech_note09186a00800b6e1a.shtml

should give you an idea as how the pix does it.

if your example, it totally depends on the configuration, but if you only have 1 legit external ip, you have to configure pat, as you do not have enough addresses to do nat

Cisco Employee

Re: NAT versus PAT

5 REPLIES
Cisco Employee

Re: NAT versus PAT

PAT is for single external IP address, mapping to multiple internal IP addresses.

Logially one IP can be used for PATting 65535 internal IPs. (as the numbers of ports available).

NAT is a one to one translation.

Thanks

Nadeem

Silver

Re: NAT versus PAT

Basically, what Nadeem said but with this one bit of real world advice:

For every 10 people who say they are doing NAT, there is actually one person doing NAT. The other 9, have one legitimate ip address (i.e., on a cable or dsl line), and are thus in fact doing PAT.

So, when people say they are doing NAT, you only roughly know what they generally mean, as often they are doing PAT. When someone says they are doing PAT, they probably mean it.

New Member

Re: NAT versus PAT

Thanks for the reply. So, if I have 3 internal hosts connected to the 'inside' of a routerwhich routes to the internet. Would those devices be nat'd at the router or pat'd? Because some people describe it as NAT and that's what confuses me. Could you send me a link with some examples?

Silver

Re: NAT versus PAT

http://www.cisco.com/en/US/customer/products/hw/vpndevc/ps2030/products_tech_note09186a00800b6e1a.shtml

should give you an idea as how the pix does it.

if your example, it totally depends on the configuration, but if you only have 1 legit external ip, you have to configure pat, as you do not have enough addresses to do nat

Cisco Employee

Re: NAT versus PAT

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