What is CGNAT?

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Carrier-Grade Network Address Translation (CGNAT) is a technology used by Internet Service Providers (ISPs) to extend the life of IPv4, the current protocol for internet addresses. Due to the limited number of IPv4 addresses, CGNAT enables multiple customers to share a single public IP address.

CGNAT works by assigning a private IP address to individual users within a network. These private addresses are then translated to a single public IP address when accessing the internet. This process is similar to traditional NAT (Network Address Translation) but on a larger scale, hence the term 'Carrier-Grade'.

A common usage of CGNAT is for mobile phone towers. Every phone connecting to the tower gets a private address and the tower presents to the internet as a single IP address.

What are the implications of CGNAT for users?

Users under CGNAT may experience challenges with services that require unique IP addresses or port forwarding, like certain online games or hosting servers. However, for general web browsing and streaming, CGNAT has minimal impact.

What are the implications of CGNAT for security providers?

CGNAT can complicate efforts to trace online activity back to a specific user, as multiple users share a single IP address. This can make blocking by IP address or rate limiting ineffective or undesirable as by blocking a single IP address you may be inadvertently affecting many legitimate users, not just the one abusing your service.