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G3100 and Hairpin NAT (NAT loopback)

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Contributor
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Posts: 2
Registered: ‎01-11-2021

G3100 and Hairpin NAT (NAT loopback)

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It is very annoying that the G3100 router does not have Hairpin NAT (NAT loopback) enabled. This is a common feature found on almost all routers including the G1100.

 

Hairpin NAT says that if I use the external IP to access the router from inside the LAN, then it should behave the same as if I had accessed the router from outside the LAN. That means apply the port forwarding and mapping to the request.

 

This is very annoying to me because I have an app on my phone that uses the external name for my network. This app works fine outside of the house. When I am inside the house the phone switches onto wifi. This causes the mobile app to stop working. Why? Because the mobile app is using the external name for the router and it is expecting port 443 to get forwarded. Since the G3100 does not have Hairpin NAT enabled the ports don't get forwarded and the app stops working.

 

This should not be happening. My mobile app should work the same whether it is external or internal to the network.  Please enable this feature on the G3100.

 

Reading around the forum I see other people experiencing similar issues without knowing what caused the problem.

 

Edit: I got my app working by moving to another port.  Reddit post clued me into Hairpin NAT works on ports besides 80/443 on G3100.

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Contributor
Contributor
Posts: 2
Registered: ‎01-11-2021

Re: G3100 and Hairpin NAT (NAT loopback)

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I got my app working by moving to another port.  Reddit post clued me into Hairpin NAT works on ports besides 80/443 on G3100.  I was using 443.

 

I suspect Verizon using 443 for external router management which is why I can't change it.

 

Why is this important? Because SSL certificates have the domain name in them. And you want to use that domain name internally so that the app won't error out with a certificate error.

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Silver Contributor V Silver Contributor V
Silver Contributor V
Posts: 611
Registered: ‎09-06-2020

Re: G3100 and Hairpin NAT (NAT loopback)

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While it would be nice for the G3100 to have this feature, but hairpin NAT is really kind of an unpopular protocol/feature.

 

The app/device responsible for sending an IP packet should determine whether the resource is on the same network or beyond the gateway. Always switch if you can, route is a secondary option.

 

What app are you using?

Contributor
Contributor
Posts: 2
Registered: ‎01-11-2021

Re: G3100 and Hairpin NAT (NAT loopback)

Message 3 of 3
(168 Views)

I got my app working by moving to another port.  Reddit post clued me into Hairpin NAT works on ports besides 80/443 on G3100.  I was using 443.

 

I suspect Verizon using 443 for external router management which is why I can't change it.

 

Why is this important? Because SSL certificates have the domain name in them. And you want to use that domain name internally so that the app won't error out with a certificate error.

View solution in original post

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