What is Nat Loopback, Enabled or Disabled?

[revolultrablue]

What is nat loopback and should i have it enabled or disabled. It's on my as88u router with merlin firmware. It's options are disabled, asus, and merlin. I have computers, a security camera, and phones on my network wirelessly only. Any help would be appreciated!

 

[bill001g]

The name I have seen that called is hairpin nat. If for example you had a port mapped port 80 to a internal web server and then assigned your wan ip to a domain like xxx.xxx.xxx.com. So for someone to open the web page they would get the ip of your wan port from the DNS and then open the server. The nat would translate the address into the internal server.

The problem comes if you try to open the web page from a internal machine. If you use the DNS name you will get the external IP when what you really want to do is connect to the internal ip directly. So your machine gets the external WAN ip and assumes it is some unkown machine on the internet and send it to your router. The router in the default configuration will send the traffic out into the internet and get it sent directly back. What happens is both the sending ip and the receiving IP are the same. Unless the router has this special function it assumes this is not a valid condition and drops the data.