Types of NAT
Types of NAT
|
Source NAT |
All callers look like they come from the same IP address |
|
Destination NAT |
Which internal address should traffic to a given port be forwarded to? |
Four types of NATs [Keyes 2004]:
|
Type |
Description |
|---|---|
|
Full Cone |
maps a specific internal IP address and port number to a given external IP address and port number This is the only type of NAT that allows an external host to contact an internal host (i.e., behind the NAT) without having previously received packets from this internal host. |
|
Restricted Cone |
external hosts must have the IP address of an internal host prior to communicating with this internal host |
|
Port Restricted Cone |
external hosts must have the IP address and port number of an internal host prior to communicating with this internal host |
|
Symmetric |
assigns unique internal IP address and port numbers based on the specific internal destination |
Slide Notes
Lawrence Keyes, “A Low Density Voice Over IP Gateway”, Master of Science in Information Technology thesis, Rochester Institute of Technology, B. Thomas Golisano College of Computing and Information Sciences, May 17, 2004 http://www.mxdesign.net/voip/voip/onfolio-files/Low%20Density%20Voice%20Over%20IP%20Gateway.pdf Links to an external site.
Transcript
[slide369] Well, as I said, the problem of NATs are not simple, because we have full-cone NATs, restricted-cone NATs, port-restricted-cone NATs, and symmetric NATs.