Question NAT test - what NAT does it see from Internet?

[mmp09]

Hi,
There's a NAT test available at https://tomchen.github.io/symmetric-nat-test/

It shows normal NAT in my case. My ISP offers me Public IP.
So does it show what NAT my WAN router has deployed?
if I were to have private IP for example then ISP is going to put me behind their own NAT
In that case will this test show me what type of NAT ISP router has or will it still show my router's NAT type? I am a bit confused how this test works. Thx

 

[EyyMunchian]

Hi,
There's a NAT test available at https://tomchen.github.io/symmetric-nat-test/

It shows normal NAT in my case. My ISP offers me Public IP.
So does it show what NAT my WAN router has deployed?
if I were to have private IP for example then ISP is going to put me behind their own NAT
In that case will this test show me what type of NAT ISP router has or will it still show my router's NAT type? I am a bit confused how this test works. Thx

Yes your router has a type of NAT automatically preconfigured. Your ISP only provides you your public IP, your private IP is configured by the local server (or router most likely in your case). Internal IPs are all local and assigned at random by DHCP unless you preconfigure Static IPs (which the average individual does not). Your NAT type can be changed by going into your router's admin panel if you wanted.

 

[bill001g]

Have no clue what that tool is calling "normal". What almost every consumer router implements is symmetric so won't that be "normal?"

In any case if you have a ISP doing nat you now have 2 NAT routers in the path. So whatever that term means it could be different on each router.
I guess it depends what it is testing for but I would suspect it is not going to be valid if you have 2 or more nat routers in the path.

It really doesn't matter almost every consumer router function in what is commonly called symmertic and you have no option to run anything else.
A lot of the other stuff some other forms of nat do is done with a feature called UPnP on consumer routers if the application supports it.

 

[mmp09]

Thank you for your answers. I think I get some idea what that user who developed that tool intended for. The user seem to have developed an online multiplayer game and the issue is it can not connect two users on internet who are both behind symmetric NAT. This is termed as Bad NAT (prevents multiplayer gaming on net) by that user.

So they think NORMAL is asymmetric NAT. That's what is reported in my case.

So what I am confused is what NAT it actually sees, is it my router or ISP's device if any?

 

[bill001g]

There are many solution for gaming between 2 users that are both on NAT. Things like port forwarding or UPnP is used to solve that problem. It would more be some application that did not use something like UPnP wouldn't work. Stuff like VoIP where the ports are dynamically generated.

That though is not the problem most people see. If you have a public IP you can use tricks like this to get around it.

It is where people do not have a public IP and the carrier is doing the NAT you have big issues. Since you have no ability to change the ISP equipment there is no way do stuff like port forwarding to run.

Again I don't know what that tools is testing for.

 

[EyyMunchian]

Thank you for your answers. I think I get some idea what that user who developed that tool intended for. The user seem to have developed an online multiplayer game and the issue is it can not connect two users on internet who are both behind symmetric NAT. This is termed as Bad NAT (prevents multiplayer gaming on net) by that user.

So they think NORMAL is asymmetric NAT. That's what is reported in my case.

So what I am confused is what NAT it actually sees, is it my router or ISP's device if any?

I'm not sure I understand the question but technically NAT sees everything. It takes packets directed toward your public IP and translates them to the correct private IP. Thats how you are able to have more than 1 device access the public internet on a single router. NAT takes your private IP and stores it into address tables, so when you send or receive information from the web you can use a routable public IP via your internal private ip. NAT basically solves the 4 billion maximum IPv4 issue. Its one large translator from web to local and vice versa.

 

[mmp09]

Unfortunately I am not able to explain it probably due to lack of knowledge. if I say 'I am behind symmetric NAT' does it imply the type of NAT from my device to the public Internet?

Is it possible that my router is using cone-NAT but ISP's device or gateway is using Symmetric NAT? If so what type of NAT is it for me?

Excuse me for my ignorance. Thx

 

[bill001g]

The nat type actually has nothing to do if the IP are public or private it purely a function of how what "source" port numbers are placed into the nat table. The IP is always translated to whatever IP is on the wan port it doesn't matter if the IP is public or private.

The type of NAT you run on your router when there is a ISP router also running NAT in front of it makes no difference. The ISP will generally run a form of symmetric nat. It generally prevents any incoming session from being initiated.