Trying to port forward but my ISP say it can ONLY be done with static ip

Question

Trying port forwarding but ISP says it can only work with a static ip

I was trying to port forward my apache2 server from my arch Linux device, I hosted my server on my ipv4: 192.168.1.5 and on default port 80. When I tried to port forward my server it didn't worked, I entered my ip 192.168.1.5 and in "from port to port" I entered 80 80 respectively. But it didn't worked, I called my ISP to resolve the issue, he told I need to buy and static ip in order to make port forwarding work perfectly, I asked them that I want to port forward with my dynamic IP for testing purpose but he told me that their network work on natting so I can only port forward if I have a static ip. I just want to know that is it true? Do I really require Statics ip in order to portforward, as far as I know we can also do it in dynamic IP, correct me if I am wrong.

• Ramhound: It sounds like you are behind a CGNAT. If that is the case, it is indeed true, you need to NOT be behind a CGNAT to sucessful host a service on your connection.

Answer 1

Yes, kind of. There is some additional hidden meaning behind "dynamic IP" vs "static IP", though.

There are at least two possible reasons why the distinction could matter:

1. Most common case: The reason why your address is "dynamic" isn't merely that it's...dynamic, but that it's handled by a CGNAT system instead of being assigned directly to you.

   Many ISPs now implement CGNAT in order to conserve their IP addresses (which have become quite expensive over the past few years – a /24 with 256 addresses goes for 11ドルk). The address that you think you have isn't actually assigned to your router anymore; it's assigned to the ISP's CGNAT system and may be shared by several customers.

   In this case, the ISP's network is set up so that assigning a static IP address automatically puts the customer in a different subnet, which doesn't go through CGNAT; paying for a "static IP" means paying for your own dedicated public IP address in general (i.e. covering the ISP's costs of having to issue you the address).

2. Less common: The ISP may just be deliberately blocking inbound connections to dynamic IP addresses. In this case, paying for a "static IP" also means paying for the inbound block to be removed – an opportunity for the ISP to get more money from you.