CGNAT (Carrier-Grade NAT)

CGNAT is provider-operated address translation that lets many subscribers share a smaller set of public IP addresses. CGNAT stands for Carrier-Grade Network Address Translation and applies the same broad idea as home-router NAT at an internet provider’s scale.

A subscriber may have a private or shared address on the provider network. When traffic goes to the public internet, the carrier translates it to a public address and port, then keeps enough state to route replies back to the right subscriber. Mobile carriers commonly use this design, and fixed-line providers can use it when public IPv4 addresses are limited.

Because many unrelated customers can appear behind one public IP, address reputation becomes shared. Abuse by one user may cause challenges or restrictions for others, while destinations may hesitate to block the address broadly because that would affect legitimate subscribers. Inbound connections are also harder because a subscriber does not control the carrier’s outer translation mapping.

Mobile proxy exits often use carrier addresses behind CGNAT. That network context can make an IP look like ordinary mobile traffic, but it does not hide browser fingerprints, accounts, cookies, or request behavior.

Related terms: NAT and mobile proxy.