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My modem|router model is : TP-LINK TD-W8961ND adsl2+ modem router


This is my modem panel page

  • cgn ip address is 100.104.5.98
  • public ip address is 86.57.91.250

I config nat ip forwarding as follows :

Ports forwarded to 192.168.1.102 :

So ports 888 , 22 , 21 should be forwarded
this ports forwarded correctly with requesting to ip 100.104.5.98

As follows :

Forwarded port 888 : working : OK

Not forwarded port 88 : not working : OK

I use iptables command to log forwarding :

while : ; do clear ; sudo iptables -L -n -v ; sleep 1s ; done

and results as follow :

So ip forwarding configured correctly .

but sending data to public ip as folllows :


from googling "what is my ip"

after sending data to public ip in port 888 recived packets from port 888 count doesn't change to 2 :

I called to my ISP and they said they don't block input connections any port

Also i disable the modem firewall :

But I realized that after send request to modem public ip , modem outs this syslog (befor send request i cleared log):

my modem forwards my requests to cgn ip to my self but not for public ip requests .

I'm looking for a solution for communicate from global internet with my home pc . I hope you can help me !

1 Answer 1

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100.104.5.98 is not a public IP address. It's so called CGN address. Your ISP hides you behind its NAT. Try to navigate to some "my ip address" page (google for it) to see that it sees you behind some completely different address that you expected.

You probably do port forwarding all right, but the problem is that you don't have a public address in the first place.

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  • You say isp have a public ip address and my modem web requests sends to isp . Then isp get result as RELATED, ESTABLISHED connection and it sends it to my modem but not send or forward NEW connections to my modem . Like local device requests to my router my modem(adsl modem router) . My home modem is local device and isp have direct connection to internet and my modem request sends to internet and isp wait for result then sends results to my modem that it is a local device in isp network. Ip of my modem is only unique to isp sub network. So if i buy static ip address does this problem solve ?
    – MH-Rouhani
    May 30, 2022 at 0:50
  • Actually my modem don't have public ip address
    – MH-Rouhani
    May 30, 2022 at 0:53
  • If you manage to have a public address assigned to your own device (at least the one you can control yourself), you'll be able to solve this problem. May 30, 2022 at 5:05

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