Does Port Forwarding Require a Public IP Address?

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KarenPetersenSu wrote:

 Time Warner/Spectrum says many different things: 1) they do not issue public IP addresses because they are not safe 2) my modem IS properly bridged - and they reset it just in case, 3)ip addresses don't change 4)the issue is with ORBI, not them.

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Hello Karen,
Typical ISP nonsense and lies. Public IPv4 addresses are short, so more and more providers do no longer assign public IPv4 addresses to consumer contract Internet connections. Regardless, they insist to offer you a fully working Internet connection. The same ISPs blocked common ports used for remote access (like 80/TCP for a http Web Server, 443/TCP for a https Web Server, plus some more) under the argument they are giving the user more security. However, it's like a phone with a number you can use to place calls, but you can never be called. Call them up and offer them to pay half of the Internet connection bill in the future because they provide you with a half service only. And they simply don't want you to use your Internet connection for providing remote access services - it's part of thier terms and conditions. 

Same ISPs love to sell you a much higher priced business connection which does include a public IP address of course. It's all about IPv4 address shortage, the introduction of IPv6 with DSlite, and simply a rip-off. If oyur Internet connection had a public IPv4 before, and was changed, you have good chances to get a public routeable IPv4 address assigned again. If the contract is newer, good luck. 

KarenPetersenSu wrote:

Orbi tech support insists that since my ip address is private, port forwarding cannot occur AND that the problem is that my Time Warner/Spectrum dual router/modem is not bridged.

If the Internet/WAN IPv4  address assigned to the Orbi Router (connected to the cable modem, issued and assigned by the cable TV provider) is an RFC6598 - IANA-Reserved IPv4 Prefix for Shared Address Space address (assigned is 100.64.0.0/10) and if my math is right it's in the 100.64.0.0 - 100.127.255.255 range, your ISP does CGN (Carrier Grade NAT), and your Internet connection is worth less than 50%, here is the IANA assignment:

   The Shared Address Space address range is 100.64.0.0/10.

In case it's an RFC1918 - Address Allocation for Private Internets address (and there is really no other NAT router in between the cable modem in bridge mode and the Orbi Router)  they are abusing the RFC1918 private address space for provider grade NAT, here are the IANA assignments:

     10.0.0.0        -   10.255.255.255  (10/8 prefix)
     172.16.0.0      -   172.31.255.255  (172.16/12 prefix)
     192.168.0.0     -   192.168.255.255 (192.168/16 prefix)

To answer your subject question:

"Does Port Forwarding Require a Public IP Address?"

Yes.

Regards,
-Kurt.