CGNAT: Difference between revisions
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Carrier Grade Network Address Translation (CGNAT) is a form of Network Address Translation (NAT) performed by internet service providers (ISPs). It involves placing many customers behind a single publicly routable IP address, and is a workaround to partially mitigate the impact of [https://en.wikipedia.org/wiki/IPv4_address_exhaustion IPv4 address exhaustion]. | Carrier Grade Network Address Translation (CGNAT) is a form of Network Address Translation (NAT) performed by internet service providers (ISPs). It involves placing many customers behind a single publicly routable IP address, and is a workaround to partially mitigate the impact of [https://en.wikipedia.org/wiki/IPv4_address_exhaustion IPv4 address exhaustion]. This can be an issue for people looking to self-host. In a non-CGNAT setup, your home router controls the NAT between your LAN and the WAN, and thus can forward ports from LAN devices to the WAN. In a CGNAT setup, there is a second layer of NAT performed by an ISP-owned router, which does not allow you to control port forwarding, and thus prevents self-hosting. This can be worked around by using a 44Net Connect tunnel to expose a device directly to the internet using a 44Net IPv4 address. | ||
== How to tell if you have CGNAT == | |||
The Internet Assigned Numbers Authority (IANA) has designated the IP range 100.64.0.0/10 for CGNAT usage. If your router is assigned an IP address in this range, your ISP is using CGNAT. This information can be found on your router's configuration page. Using websites such as whatismyip.net or similar will not tell you whether your ISP uses CGNAT, because the CGNAT IP range is not publicly routable. This means that your router's packets originating from a CGNAT IP are relabeled with a publicly routable IP by the ISP router before they exit the ISP's network, so internet services are not able to see the CGNAT IP. | |||
[[Category:Reference]] | [[Category:Reference]] | ||
Revision as of 23:37, 28 August 2026
Carrier Grade Network Address Translation (CGNAT) is a form of Network Address Translation (NAT) performed by internet service providers (ISPs). It involves placing many customers behind a single publicly routable IP address, and is a workaround to partially mitigate the impact of IPv4 address exhaustion. This can be an issue for people looking to self-host. In a non-CGNAT setup, your home router controls the NAT between your LAN and the WAN, and thus can forward ports from LAN devices to the WAN. In a CGNAT setup, there is a second layer of NAT performed by an ISP-owned router, which does not allow you to control port forwarding, and thus prevents self-hosting. This can be worked around by using a 44Net Connect tunnel to expose a device directly to the internet using a 44Net IPv4 address.
How to tell if you have CGNAT
The Internet Assigned Numbers Authority (IANA) has designated the IP range 100.64.0.0/10 for CGNAT usage. If your router is assigned an IP address in this range, your ISP is using CGNAT. This information can be found on your router's configuration page. Using websites such as whatismyip.net or similar will not tell you whether your ISP uses CGNAT, because the CGNAT IP range is not publicly routable. This means that your router's packets originating from a CGNAT IP are relabeled with a publicly routable IP by the ISP router before they exit the ISP's network, so internet services are not able to see the CGNAT IP.