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Not much i can specify here - its obvious that my CPE is NATing my LAN, but how do i find out if my ISP is using a carrier-grade NAT (obviously, without asking them)?

I heard that port forwarding is not working in multi-level NATs, and that you need STUN/TURN for that, and portforwarding works just fine for me, so i could assume that my ISP is not CGNing?

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  • Unfortunately, questions about home networking are explicitly off-topic here, You could try to ask this question on Super User.
    – Ron Maupin ♦
    Mar 11, 2019 at 13:56
  • I never said that this is about home networking, this could very well be a company related question (it is, in fact, not about my home network.)
    – Flying Thunder
    Mar 11, 2019 at 13:58
  • CGNAT is used for residential/home networking.
    – Ron Maupin ♦
    Mar 11, 2019 at 14:02

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You need to connect a host to the router you have directly connected to your ISP.

Navigate to http://myip.dk/ or a similar service, that will reveal your public IP address.

Now login to your router and check what public IP address it has configured either via DHCP or static configuration.

If the two public IP addresses are the same, then your ISP is not using CGN.

If your ISP is using CGN it would typically show a WAN IP address like 100.xxx.xxx.xxx, 10.xxx.xxx.xxx. or 192.xxx.xxx.xxx.

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