CGNAT (Carrier Grade Network Address Translation)

Carrier Grade NAT lets a single public IPv4 address be shared by many subscribers, mitigating IPv4 exhaustion. While necessary in IPv4-only deployments, CGNAT complicates abuse attribution (multiple subscribers behind one public IP), undermines lawful-interception logging precision, and causes problems for inbound services. IPv6 deployment is the long-term answer.

Categories: Identity and SubscriberThreats and AttacksInternet and Routing

CGNAT in context

Subscriber identifiers (IMSI, SUPI, MSISDN, IMEI) anchor authentication, charging and lawful interception. Any protocol that leaks a permanent identifier is treated as a privacy defect, which is why 5G introduced SUCI concealment on the air interface.

Telecom threats range from opportunistic SMS phishing and SIM swap to nation-state grade location tracking. The common thread is that most attacks exploit the inherited trust model of legacy signaling protocols.

To place CGNAT in the wider telecom-security picture, review Sinkhole, A5/2, Artificial Traffic Inflation, ASN, BGP and BGP Hijacking — each entry cross-references back to this page so you can walk the topic in either direction.

Related terms

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