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All productsWhat is NAT?
NAT is a widely used technique in home and business networks to enable multiple devices to share a single public IP address. It allows devices within a private network to communicate with public networks without requiring each device to have its own unique public IP. Initially introduced as a temporary solution to address the limited availability of IPv4 addresses, NAT effectively conserves the pool of publicly routable IPv4 addresses by mapping multiple private IPs to a single public IP.
Meanwhile, although IPv6 offers a vast address space to meet modern network demands, many networks require IPv4 and IPv6 to coexist. NAT plays a crucial role in supporting this coexistence, enabling communication between IPv6-only and IPv4-only devices through mechanisms like NAT64 translations. This capability ensures seamless connectivity and compatibility during the transition from IPv4 to IPv6.
What is CGNAT?
CGNAT is an advanced form of NAT employed by ISPs to provide internet access to customers while conserving the dwindling pool of IPv4 addresses. CGNAT enables multiple customers to share a single public IP address by assigning unique port numbers to each customer’s device, similar to the Port Address Translation (PAT) mechanism. This approach allows ISPs to maximize the use of limited IPv4 resources while maintaining connectivity for a growing number of users. For example, VSUF-160 and VSUF-80 of Huawei ME60/NE40E series routers provide CGNAT function.
As the exhaustion of IPv4 addresses continues to pose challenges, ISPs increasingly rely on CGNAT as an interim solution while transitioning to IPv6, which offers a vastly larger address pool. Although IPv6 adoption is progressing, CGNAT remains a critical tool for addressing the IPv4 shortage in the meantime.
Differences between NAT and CGNAT
While both approaches enhance IPv4 utilization, they differ in various aspects, such as implementation, scalability, and impact on user experience, creating unique advantages and challenges for network administrators and service providers. Let’s take a closer look at both of them.
| NAT (Network Address Translation) | CGNAT (Carrier-Grade NAT) | |
| Purpose | Used for translating private IPs to a single public IP, primarily for home or small office networks. | Used by ISPs to extend IPv4 address pools by sharing public IPs among multiple users. |
| Scale | Small scale, typically limited to individual routers or networks. | Large scale, implemented at ISP level to manage IP scarcity. |
| IP Address Sharing | Typically assigns a unique public IP to each network. | Shares a single public IP among multiple customers or users. |
| Privacy and Security | Offers basic security by masking internal IPs from external networks. | Offers some security but can complicate tracking of individual users. |
| Performance | Minimal impact on network performance for small networks. | Can introduce latency and affect performance due to address sharing. |
| Port Limitation | Allows most applications to use any port needed. | Limited number of ports per user, which can cause conflicts in applications. |
| Configuration Complexity | Simple configuration for small networks. | Complex configuration, often requiring specialized equipment. |
| Ideal Use Cases | Home networks, small offices, or private networks. | Large ISPs or mobile network operators managing millions of users. |
| Impact on IPv6 Transition | Slows IPv6 adoption, as NAT works with IPv4. | Further delays IPv6 adoption due to reliance on IPv4 extension. |
As you can see from the above, CGNAT is a subset of NAT. Normally we would think of NAT as a technique for converting private network addresses to public network addresses, but in fact, NAT encompasses many more possibilities.
