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" I highly recommend John Greenwood - he has done amazing things with mine and my husbands computers at a very reasonable price, to include fitting a new hard drive, anti-virus, generally cleaning it up, and all the little things that annoyed me but I didn't know how to fix. "
GY - Hythe |
Possibly not the most technically accurate document I've ever written, but I'm hoping it makes something very complex a little more understandable.
IP Addresses (IPv4 in particular)You've probably seen an Internet Protocol Address (IP Addr), and unless you're a real nerd, you've ignored it - but they are important :-)
Think of an IP address as an internet phone number, it identifies your device, and so needs to be globally unique.
The unique E164 format phone number, +442380986954, will only ring the phone on my desk in the same way that IP address 77.68.14.146 will only connect to this web server. NAT - Network Address Translation
Traditionally, many small businesses had their own small telephone exchanges in their office. This allowed external people to call in, and the call could then be passed to the correct telephone within the building.
This allowed the business to have dozens of phones on desks, but perhaps only have one incoming phone number. This meant that businesses didn't have to publish the number of every desk, as the company operator would 'route' your call to the correct desk.
This is exactly what your broadband router does, it has one public IP address (yours looks like it's 44.220.251.236) and it routes the various incoming traffic to your device inside the building. When someone rings a phone number, or connects to your IP address, they have no idea how many extensions (employees) or computers you have inside your building.
The router needs to just remember which traffic is destined for which device - this remembering and re-routing is the core NAT functionality. CGNAT - Carrier Grade NAT
So CGNAT is basically double-natting the traffic. This clearly works for web browsing, as you are reaching out from your device and each NAT router is remembering you asked for this traffic, so when I send this text back, it should get to the right computer!
However, what if I wanted to initiate a link to your machine? What if you run an email server or a CCTV camera system? The two NAT routers have no 'memory' on how to get the informtion to the right target machine as there was no outgoing request a few seconds before. Testing for CGNATIf you're on any version of Windows, then it's very easy. We just need to ask your router if it's IP address matches who I think you are. Just start a CMD shell and type;
If the line in red does not show your IP address, then you know you have a CGNAT situation. If you do want to access various services remotely, then you will need to speak to your internet provider about getting a 'Public IP Address' - I can help. |
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