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I've been working with my ISP to open some ports on my JioFi 3 MiFi device (a pocket-sized WiFi router that runs on a SIM card, often locked to the SIM provided by the company that makes the router.)

Recently Jio have launched their own MiFis devices, using UDP port 11155. All goes fine, I can just go and type in my local IP, the port range, and select the protocol and the port should be open, except that it is not.

Also, by default, my MiFi shows an IPv6 address as my public address, so I disabled IPv6 to only have IPv4 to work with.

The WAN IP, as shown on my router config page, is different from my Public IP as reported by Google searches and Whatismyip.com.

The proxy test on my Whatismyip.com detects no proxies. My ISP can set up port forwarding perfectly using the same device and procedure that I am using. But since my public IP and WAN IP don't match, I have a reason to suspect that the problem is on the ISP side.

However, could it be possible that something on my end is blocking my connection? I have no additional routers. Also, I have an almost fresh installation of Windows 10 Home. I'd like to be sure that there is no issue on my end before I rant my ISP again.

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  • What is your WAN IP? Does it fall in one of these ranges? 10.0.0.0/8, 172.16.0.0/16, 192.168.0.0/16? If so, the difference between WAN IP and public IP is absolutely normal. Apr 6, 2017 at 7:38
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    Is there a point in port-forwarding if you already have IPv6? Apr 6, 2017 at 7:39
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    The reason for the discrepancy in IP addresses is probably because the ISP is using CGNAT (Carrier Grade NAT) to preserve their pool of public IP addresses. Not sure this would show up in a proxy test, because it's not a proxy.
    – Darren
    Apr 6, 2017 at 8:46
  • @grawity I didn't get you?
    – YaddyVirus
    Apr 6, 2017 at 16:34

1 Answer 1

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This is because Jio is doing Double NATing.

NAT (Network Address Translation) allows your devices to share a single WAN IP address (provided by your Internet Service Provider) by changing the public IP address to a private IP address. This process also secures your network by blocking any direct access to your local IP address.

Double NAT is when you connect your router behind another router creating two different private networks. For example, connecting your NETGEAR router behind a modem/router provided by your ISP. Double NAT does not prevent your devices access to the internet but may cause problems with playing online games, opening a specific service port, connecting to a VPN tunnel, or visiting secure sites with SSL. Also, the devices connected to the first private network may not be able to communicate to the devices connected to the other private network.

https://kb.netgear.com/30186/What-is-Double-NAT

I recently saw another user's post about this problem on UNIX stackexchange: https://unix.stackexchange.com/questions/408639/how-to-configure-a-noip-on-linux-if-i-has-double-nat-isp-like-jiofi

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  • I did figure that out eventually... But thanks for the elaborate explanation
    – YaddyVirus
    Jan 13, 2018 at 6:20
  • @yaddyvirus were you able to resolve the issue I am facing the exact same issue and don't know how i can port forward. both port-forward and upnp doesnt work as my no ip dynamic dns cannot connect to the device. Jul 28, 2021 at 3:37

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