With the official depletion of IPv4 addresses in North America, Carrier Grade NAT has emerged as a solution for large organizations to accommodate and translate between private addresses and shared public addresses. Is this an issue for your organization? Let’s examine the issue as well as the solution.

1. What is IP Address exhaustion and what’s the difference between v4 and v6?

IPv4 address exhaustion is the depletion of the pool of unallocated IPv4 addresses.

An IP address is a set of binary numbers but can be stored as text for human readers. For example, a 32-bit numeric address (IPv4) is written in decimal as four numbers separated by periods. Each number can be zero to 255. For example, could be an IP address.

IPv6 addresses are 128-bit IP address written in hexadecimal and separated by colons. An example IPv6 address could be written like this: 3ffe:1900:4545:3:200:f8ff:fe21:67cf

2. What happened to overextend or over-allocate IP addresses to certain entities?

In the 1980’s, some organizations were allocated many more IP addresses than they could use. Class A address blocks were assigned to many large institutions, giving them over 16 million IPv4 addresses. While the next class, Class B blocks, received only 65,536 addresses each, much too small for many universities and large companies.

IPv4 address depletion was predicted as far back as the early 1990’s, and yet no one could have predicted the tremendous growth of the internet, nor the vast numbers of personal devices in the hands of most of the North American population.

The American Registry for Internet Numbers (ARIN) issued a statement on 7/2/2015 that America had officially run out of IPv4 addresses.

3. What is Carrier-Grade NAT (or Large-Scale NAT)?

Traditionally, NAT (Network Address Translation) was used for translating the address ranges between two networks. Carrier-Grade NAT takes it a step further as a way to address the scarcity of IPv4 addresses available, by sharing a global (public) IP address among several local (private) IP addresses.

“NAT is the technology that has for many years prolonged the life of IPv4 by serving as the translator between private IPv4 addresses on a local network and shared public IPv4 addresses. Were it not for the widespread use of NAT44, as it is known, IPv4 addresses would have been used up many years ago, as once predicted.” (

Internet Service Providers and Higher Education are the top two organizations that have already or may have to consider looking at Carrier Grade NAT solutions.

According to APNIC, the Regional Internet Registry serving the Asia Pacific area, “Carrier Grade NAT (CGN) and Large Scale NAT (LSN) are often presented as ‘IPv6 Transition Technologies’. In reality CGN, LSN, or any other mechanisms that provide IPv4-to-IPv4 connectivity on Network Address Translator (NAT) platforms (i.e. NAT444) are NOT transition mechanisms to IPv6. They are technologies to prolong IPv4 address availability by using private IPv4 address space in Service Provider (SP) networks.”

4. What does IP Networks recommend?

IP Networks provides two different solutions in the Carrier Grade NAT marketplace. One of those solutions is dedicated to handling Carrier Grade NAT only and the other solution has Carrier Grade NAT (NAT44 support only) as an add-on license.

Customers who need to consider Carrier Grade NAT should pick two or three different solutions and bring them in-house to evaluate how they perform. Customers need to make sure that whatever solution they decide upon is solid and stable in preventing applications/service from “breaking”.

IP Networks makes the evaluation process as painless as possible. We assign a senior sales engineer to help assist throughout the entire testing process from racking and powering the equipment/software, configuration, and giving the customer information on how to use the platform. We always ship brand new equipment so that if the customer is pleased with the evaluation they can keep the equipment in place.

The A10 Networks brand Carrier Grade NAT solution that we provide is half the price or more of the competition in the market. A10 has been doing Carrier Grade NAT for over 10 years.

Many Tier 1 and Tier 2 Service Providers along with Tier 1- and Tier 2-sized Higher Ed’s are deploying A10’s Carrier Grade NAT solution because it is more cost effective, has excellent reporting capabilities, and comes in a 1U size form factor or as a Virtual solution for VMware.

5. Pros and Cons of Carrier Grade NAT

Pros of Carrier Grade NAT

  • CGN allows you to open up more IPv4 address space for future use.
  • It preserves IPv4 address space. This is called NAT44.
  • It allows for IPv4 and IPv6-addressed machines to be able to communicate with each other via several Carrier Grade NAT methodologies such as:
    • NAT 6rd – allows for IPv6 migration
    • Stateful NAT64/DNS64 – allows for IPv6 migration
    • Stateless NAT46 – allows for IPv6 migration
    • DS-lite – allows for IPv6 migration
    • Lw-4o6 – for IPv6 migration

Cons of Carrier Grade NAT

  • If you have a solution that does not have accurate and robust reporting it will be very difficult to track everything so that in a CGN environment you know who has what IP address(es).
  • Many customers complain of how much disk space is required for logs and reporting with CGN solutions. The A10 Networks solution offered through IP Networks has features built into it that has allowed them to cut down on the amount of disk space required.
  • Lastly, CGN, if not set up properly or developed by the manufacturer properly, can break applications or services making them unavailable to network users/devices