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NAT Terminology question

S

subflava

Senior member
Anyone know what terms are generally used to describe "reverse NAT'ing"?

Normally when people use "NAT" they mean that source addresses are translated (usually private IP's to a single internet IP) at a router device. What do you call it when you translate the destination address instead? Destination NAT? Outside NAT? Inside NAT?
 
translate the destination address? Depends on the destination...the destination of packets coming into your network...or the destination of packets leaving your network.
 
there's nat which only deals with the IP address - ie it only modifies the layer 3 info.

There there port address translation - which modifes the layer3 and layer 4 info.

Most of the times nat is just for outbound connections like a client starting a TCP session with a web server. The source address is changed, and the ensuing reply from the server's destination address is changed.

PAT works the same way except the source port is changed as well. used when there is more than IP inside ip address being used.

In cisco terms what you're describing is a "static" NAT and is used for machines that will be receiving connection requests like servers. An outside address is translated to an inside address.
 
Linux netfilter calls them SNAT and DNAT, or Source NAT and Destination NAT.

When most people say NAT they really mean PAT.
 
lol...guess I'm not being clear judging from the responses. Sorry, let me try again.

Normally when people use "NAT" they mean that source addresses are translated...
Click to expand...

Oops. I realized I asked the question wrong because I wasn't thinking of the process correctly. When you're talking about NAT in the common scenario (ie. Some office computers with private addresses behind a router trying to reach a website on the internet), the outgoing packets from the workstations get their SOURCE IP addresses changed (yes I know technically there is also PAT being done in this scenerio, but let's just ignore that for my question) and the incoming packets from the webserver get their DESTINATION addresses changed when they hit the router. I was thinking the source addresses get translated in *BOTH* directions which obviously doesn't make sense.

In cisco terms what you're describing is a "static" NAT and is used for machines that will be receiving connection requests like servers. An outside address is translated to an inside address.
Click to expand...

After reading the above I realize the stupidity of my question. I knew the answer all along..."static mapping/static NAT".

I've probably just confused more people like I was confusing myself, but thanks for the help guys.
 
and the incoming packets from the webserver get their DESTINATION addresses changed when they hit the router. I was thinking the source addresses get translated in *BOTH* directions which obviously doesn't make sense.
Click to expand...

Both do get changed in that scenario, because the webserver has a private address the router/firewall has to NAT it's address in the replies.
 
Both do get changed in that scenario, because the webserver has a private address the router/firewall has to NAT it's address in the replies.
Click to expand...

?? Are you talking about the other end of the connection? Well, assuming the webserver also has a private IP and sits behind NAT then you're right.
 
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