#1 Go to
http://whatismyipaddress.com/#2 On that web page is the non bogan IP (Public) Address that users from Internet use to connect to you.
#3 In your router, you must have the same non bogan IP Address.
#4 If your router you do not see the non bogan IP Address, it first depends on the WAN IP in the router.
a) If the WAN IP in the router is in the IP Address Range of 100.64.0.0 - 100.127.255.255, then CGNAT/NAT444/LSN is present.
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If you want more details about CGNAT/NAT444/LSN, you can look at
http://en.wikipedia.org/wiki/Carrier-grade_NATThe possible fixes to fix your issue if CGNAT/NAT444/LSN is present.
#1 Have them in their NAT router forward the ports to the IP of your router..
#2 Upgrading the type of plan that you are on with your ISP so that you get a non bogan IP Address.
For example if you are a Residential Service Plan, consider going to a Business Service Plan.
#3 Consider switching to another ISP that can give you you a non bogan IP Address.
#4 For the long term future, get IPv6 working.
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b) If the WAN IP in the router is any of these IP Address Range(s):
From 10.0.0.0 to 10.255.255.255, from 172.16.0.0 to 172.31.255.255 OR from 192.168.0.0 to 192.168.255.255 now it matters the type of NAT router it is.
-> Based upon your type of router, CGNAT/NAT444/LSN is present ( see above for fix ).
d) If the WAN IP was not any of those, it would be a good idea to check to see how the non bogan IP Address is not the same (and not NAT). If users need help finding why that is, they are to asking for help doing so.