> Can someone please explain to me the difference between NAT and >PAT.
NAT is the direct translation of one IP address to another. As an example,
let's say you had a /28 block of external registered addresses (let's use
200.10.10.0/28, I have no idea who that really is) and you're using the
10.0.0.0 private network addresses inside. If you were using NAT only, the
first device requiring an outgoing internet-routable address from your
network would get one IP address from your /28. The next device would get
another IP address from the pool. However, once you've used up your 14
usable addresses, you're in trouble; you have no more addresses left.
Now, if you were using PAT in conjunction with NAT, the first 14 addresses
would be assigned in the same way as the first example. The difference is
what happens when the next device requires an IP address.
Let's say the 14th request for an address was user IP 10.1.1.1 browsing the
web. His source IP is 10.1.1.1, and source port is 4684 (just for grins.)
When this IP is translated, the port is translated as well, so you might end
up with a mapping like 10.1.1.1(4684) to 200.10.10.14(65001). So, the
outside world would see that last IP/port combo as that user.
Now, another user wants to do some web surfing and they need an outside
address. Let's say they are 10.1.1.42(5812). They would be translated to
the *same* IP address as the previous person, 200.10.10.14, but to a
different port, perhaps 65002 (I'm being very arbitrary about these numbers,
but you get the idea.)
This allows you to have FAR more than 14 users without requiring you to get
a larger block of assigned addresses. Using NAT and PAT, you could quite
easily handle hundreds of users with only a /28 block of public addresses.
I hope that makes sense. It's early and I'm only on my second cup of
coffee. :-)
John
_______________________________________________________
Send a cool gift with your E-Card
http://www.bluemountain.com/giftcenter/
_________________________________
FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html
Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
