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access internal server with external address

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access internal server with external address

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access internal server with external address
access internal server with external address
2012-11-07 16:18:14 - last edited 2021-08-21 03:05:02
Region : Netherlands

Model : TL-R470T+

Hardware Version : Not Clear

Firmware Version :

ISP :

Hi,

my current router does not allow me to access internet servers using external ip address from inside the network, because the router thinks I am trying to access the router instead of wanting to access a forwarded port.

Basically, if my external IP is 24.132.133.180 and my internal network is 192.168.0.0, and my router is at 192.168.0.1, and my PC is at 192.168.0.5

Then if I access 192.168.0.1 it should access whatever service the router is running.
But if I access 24.132.133.180 then it should access the port forwarding feature of the router.

Therefore, should my PC be running a webserver at port 80, then accessing http://24.132.133.180/ should open the webserver at my PC, and not the webserver of the router. If I have port 80 forwarded to 192.168.0.5. It should access my PC at 192.168.0.5, not the router at 192.168.0.1.

Is this possible with the TP-LINK TL-R470T+ router?
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#1
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8 Reply
Re:access internal server with external address
2012-11-07 19:55:29 - last edited 2021-08-21 03:05:02
Interesting!!! Not clear about your network topology and your internet servers. the 24.132.133.180 is your wan IP address of the R470T+, or something else ?
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#2
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Re:access internal server with external address
2012-11-07 20:37:48 - last edited 2021-08-21 03:05:02
This link is really useful: http://www.tp-link.com/en/article/?id=134
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#3
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Re:access internal server with external address
2012-11-08 11:29:11 - last edited 2021-08-21 03:05:02
The feature I am talking about is called "NAT loopback".

It is not a question about basic port forwarding. I can handle that one.

It's about being able to access the port forward from the INSIDE of the network.

Suppose my PC is at 192.168.0.5
Suppose my Server is at 192.168.0.3
Suppose the internal address of the LAN interface of the router is 192.168.0.1
Suppose the external address of the WAN interface of the router is 24.132.133.180.

Then what must happen is:

192.168.0.5 <--> 192.168.0.1 24.132.133.180 192.168.0.1 <--> 192.168.0.3

So in that case all traffic goes through the router and requires NAT translation back and forth. Suppose the desired server is a port 80 webserver. 192.168.0.5 tries to reach 24.132.133.180 port 80. The router receives this request on the internal interface (192.168.0.1). It sees that the requested destination is on the outside, so it does Source-NAT, changing the IP source address of the package from 192.168.0.5 to 24.132.133.180. Then it routes the package - to itself. It realizes the requested port requires port forwarding to 192.168.0.3, so it does Destination-NAT, changing the IP destination address of the package from 24.132.133.180 to 192.168.0.3. It then routes it to the internal interface 192.168.0.1 and sends it off.

The Server at 192.168.0.3 then receives a package from 24.132.133.180. A request for port 80. The Server responds to it by sending a package back. The Router again performs SNAT, and then again DNAT according to its tables and routes the package to 192.168.0.5.

In this way, there is performance loss, because the Router has to do NAT translations all the time. But the Server is accessible from inside the network using the external address that all other people also use.
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#4
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Re:access internal server with external address
2012-11-08 18:04:42 - last edited 2021-08-21 03:05:02
My friend has a TL-WR340G. He said that the tplink tech support told him that the TL-WR340G and all their Wired Router can support NAT Loopback function. Maybe you can send an email to them to confirm it.
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#5
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Re:access internal server with external address
2012-11-08 19:25:19 - last edited 2021-08-21 03:05:02
I was in touch with Olivia Zhang from tech support in Hong Kong probably. She ran a test for me this afternoon to check, and she confirmed that loopback works. She says they have a list of ADSL routers that support loopback, but no list for wired routers yet.
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#6
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Re:access internal server with external address
2012-11-09 18:24:16 - last edited 2021-08-21 03:05:02
Lol... now another support tech from TP-Link has also run some tests, and she confirmed that it does NOT support NAT Loopback. :S.

Meanwhile, I realized it is not a gigabit router so I can't use it for my needs anyway.
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#7
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Re:access internal server with external address
2012-11-15 12:33:39 - last edited 2021-08-21 03:05:02
I'm pretty sure TP-LINK wired routers support NAT Loopback, I have test it with my IP camera, it works.
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#8
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Re:access internal server with external address
2012-11-15 18:35:07 - last edited 2021-08-21 03:05:02
Thank you. Olivia Zhang confirmed the same. Also with IP camera.

I am probably going to install a 3rd party firmware on it though like OpenWRT, Gargoyle or DD-WRT. And I'm not getting the one I mentioned, but the TL-WR1043ND. I am glad to hear that this feature is supported natively.
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