This is a guide for people who have ongoing connection problems and have tried everything they can think of.
If you are experiencing unexplained, random dropping from matches or arbitrary changes in NAT type, this guide may help you!
If you feel that your connection configuration is correct, but you are still experiencing connectivity problems, this guide may help you!
What is Carrier Grade NAT?
Carrier Grade NAT (CGN) is basically a method that Internet Service Providers (ISPs) use to conserve IP addresses. There simply aren’t enough possible IPv4 addresses to assign a public IP address to every device (router, computer, smartphone, XBox, PS4/5, etc.).
Therefore, ISPs use CGN to allow many devices to share a public IP address. Essentially, many ISPs set up their own network and assign your device an IP within that network. They then route all your traffic through another IP that you share with other customers of the ISP.
That is, the ISP is acting like a giant router and that adds another layer of NAT to your connection.
There is no reason why ISPs may not use as many layers of networks as necessary to provide enough IP addresses to all their customers.
Unfortunately, this may cause connectivity problems for a number of reasons, especially with games.
Testing for CGN Part 1: Finding Your Public IP
Testing to see if your ISP is using CGN is not very hard.
The first thing you need is your public IP address. Fortunately, most search engines make this easy.
- Search for “my ip” in a major search engine (like Google or Bing),
- Take note of the string of numbers returned at the top (for example: 192.168.1.1).
Either write this number down or copy it, as you will need it later.
Testing for CGN Part 2: Running Trace Route
The next part is to run Trace Route on your public IP address. This is a little bit more involved, but still very easy.
This walk-through only applies to Windows machines. If you have a different OS, you will have to look elsewhere. Sorry about that!
To run Trace Route:
- Press the “Windows logo key” + “s” to open the search bar;
- Type “cmd” and select the option “Run as administrator”;
- If a dialogue window pops up, select “Yes”
- In the window that opens type “tracert your IP here“, replacing the text “your IP here” with the IP address you noted in Part 1, and press the “enter key”;
- Wait for the process to finish and return to the command prompt.
You should now see a set of numbered lines, each with a response time in ms and an IP address.
Testing for CGN Part 3: Interpreting Results
The results shown by running Trace Route on your own public IP are not 100% definitive, they are interpretive.
That said, they strongly indicate where or not your ISP is using CGN.
If you have a single line returned…
Congratulations! Your ISP is definitively NOT using CGN.
If you have multiple lines returned…
Your ISP may be using CGN.
The more lines returned, the more likely it is that your ISP is using CGN.
The caveat to this is if you have a multi-router setup at home.
For example, if you have router-modem combination device provided by your ISP, but you connected your own router to it and then connect your devices through that 2nd router; your results will probably show at least 2 lines, even if your ISP is not using CGN.
Your ISP is Using CGN: What Now?
If you determine that your ISP is using CGN, your options are:
- Contact your ISP and talk to them about it. They may be able to provide you your own public IP. On the other hand, they may not readily offer you any solution. This is an issue between you and them and beyond the scope of this guide.
- Use an alternative IP address, such as those provided by proxy or VPN services. Be aware that using such services to misrepresent your location (especially for purchasing things, including games or other software) may violate EULAs or law in some jurisdictions. You are responsible for your own actions and this does not constitute a recommendation, as such, or legal advice.
The use of CGN by ISPs is very common today. Many have yet to convert over to IPv6 (which has exponentially more IP combinations) and are thus forced to conserve IPv4 addresses.
This can cause great frustration, especially for gamers.
I hope that this guide helps to alleviate some of that frustration. At the least, I hope that it helps some of you to understand why your connectivity may have seemingly random and arbitrary problems!
Thanks for reading and good luck!