Behind Carrier Group NAT?

Hi all,

I'm looking to set up a local server, but came across the term Carrier Group NAT, which may make it impossible to do.

I have a home fibre broadband connection.

Does anyone know how I can find out if I am behind a Carrier Group NAT?

Thanks

Jim

Which provider?

Running a consumer service across CGNat is not great, as may cause issues with some services.

Why do you think you are behind a GGNat, rather than just the usual NAT that the router in your home is running, and the way to resolve NAT is to use port forwarding in the router.

I'm having issues with connectivity.

With SSE who use Daisy Communications.

Connectivity to and from what?

Have you created the hole in the local router NAT (port forwarding) so the 'server' is visible from the Internet?

Sorry, yes, I am setting up a local FTP server on Windows 10 . I have configured the firewall and router to forward the port, but unable to connect to the server through the public IP.

There are 5 IPv4 routes listed on the router (not sure what this means), so I got my public IP from a web tool.

Googling solutions raised the issue that if you're behind a NAT444/CGNAT then it is not possible to configure a local server because the port forwarding would need to be done on the ISPs network?

The public IP I have never changes, even when disconnecting, so I'm hoping it is a static IP?

It's been many years since I last set up a local server.

can you see the server locally ?

If you are on a PC on your local LAN and trying ftp <YOUR PUBLIC IP> then this won't work because NAT loopback is probably not present on your router.

To test if the FTP server is running you first do fttp <ITS LAN IP ADDRESS> if that works and then you've set up the forwarding correctly then you need to use a device NOT on your own network to see if it connect.

So nothing to do with CGNAT

In reply to a post by jimasap:

I'm looking to set up a local server, but came across the term Carrier Group NAT, which may make it impossible to do.

I have a home fibre broadband connection.

Does anyone know how I can find out if I am behind a Carrier Group NAT?

Carrier *grade* NAT just means a honking big NAT box at your ISP. It's unusual for wired ISPs in the UK, but you may see it if you are on a small or new provider. It's very common for mobile.

The way to find out is to go to your router's management interface and see what IP address it has been assigned on its WAN interface. Then go to a site like whatsmyip.org which tells you what IP address it sees your incoming connection coming from. If they are the same, then you are not behind a CGN. If they are different, then you are.

If you are behind CGN, then your WAN address will have picked up some sort of private address, which the CGN NATs to a public address. In this context, "private" does include the well-known RFC1918 ranges (192.168.x.x, 172.16-31.x.x, 10.x.x.x) but there is also a block specially reserved for CGN (100.64-127.x.x). And occasionally I've seen networks just take random bits of public IP address space and treat it as if it were private.

Sadly not going to be unusual for long - with Virgin announcing they'll be going to IPV6 using DS-Lite, so native IPV6 and CGNAT for IPV4

Is your server down steam of a domestic router using NAT? If so getting FTP to work from outside your home network is difficult. Google for 'ftp Nat'.