Explain the limitations of IPv4 that are overcome by IPv6?

With so many devices working on IPv4 addresses like computers, laptops, mobiles, appliances (Internet of Things or IoT), and the IPv4 address depletion was bound to happen. This is applied to Economics, more IPv4 demand, and less IPv4 supply.

IPv4 address size:

To start with let us first understand why IPv4 addresses are not enough? IPv4 uses 32-bit address space which amounts to nearly 4,294,967,296 unique values.

A quick calculation shows how IPv4 addresses are distributed:

  • 4,294,967,296 unique values = 256 /8
  • /8 = 16,777,216 unique address values, hence 256 * 16,777,216 = 4,294,967,296
  • Reserved IPv4 addresses used for special purposes = 35.078 /8
  • IPv4 addresses for public use = 220.922 /8 address blocks
  • (Source: ipv4.potaroo.net)

Also Read our informative blog: How many IPv4 addresses are there?

Limitations of IPv4:

Now that you know the distribution of IPv4 addresses, the RIRs (Regional Internet Registries) has no IPv4 reserve left. The following are some of the problems with IPv4 overcome by IPv6:

  • Growing IPv4 demand, but less supply: Growth of internet worldwide has increased demand for IPv4s but lack of supply of IPv4 addresses has caused companies to squander to acquire IPv4s.
  • Small Internet header length: The Internet Header Length field of IPv4 can only hold values from 0 (Binary 0000) to 15 (Binary 1111). SoHence, the longest Internet Header (IP headersize is 15*32 Bits = 480 Bits = 60 Bytes. Maximum header size = 60 bytes and shortest header size = 20 bytes.
  • IPv4 public networks can be vulnerable to communication breach: Since, initially IPv4s was designed for a closed and private US military network that was isolated, the security aspect of network communication was not a priority then and is vulnerable to breaches or hacks, however as internet became popular, it was slowly rolled out for universities and institutions for education and research purposes.
  • Service support is not qualitative: Anything you buy, you expect a high quality of support, but in IPv4 some network applications when not running smoothly is not supported.
  • IP addresses centralized in US: Since the internet was invented in the US, a large pool (nearly 50%) of IP addresses were centralized and reserved for the US only.

How many IPv6 addresses are there?

The size of IPv6 address space is 128-bits (2128). It has 340,282,366,920,938,463,463,374,607,431,768,211,456 IPv6 addresses. That means almost unlimited IPs to last us for centuries.

IPv4 vs. IPv6:

The main difference between IPv4 and IPv6 is the number of IP addresses. Take a look at the table below to know their major difference:




No. of Addresses



Internet Header Length

Maximum: 60 Bytes

Minimum: 20 Bytes

No longer needed, since IPv6 header is 40 Bytes always


Not so secure

Protection and security like VPN

Speed or efficiency

Not so fast data transfer

Simple and fast data transfer

Advantages of IPv6 over IPv4:

IPv6 was introduced to take place of IPv4 and has many advantages over IPv4, namely:

  • Bigger address size, i.e., 128-bit address or 2128
  • IP Security is in-built
  • Efficient way of handling data packets
  • Optimized way to preserve bandwidth and streamlined services
  • Simplified network administration
  • More reliable than IPv4

IPv6 disadvantages:

  • Not compatible with IPv4 devices: It may take another 10 – 15 years or more to totally replace IPv4, since it is not compatible with devices using IPv4, so basically newer devices are IPv6 enabled, whereas if these newer devices wanted to communicate with IPv4 devices, it can’t, since the developers did not develop IPv6 to support or be compatible with IPv4, rather their motive was to completely shift from IPv4 to IPv6, basically to make IPv4 redundant and use only IPv6 in the future.
  • Replacing IPv4 with IPv6 hardware: This is a very big challenge, replacing IPv4 with IPv6 hardware and equipment.
  • Investment in IPv6: Not many companies have thought about shifting to IPv6 since it requires them to invest in new equipment that supports IPv6 only. But, there will be a time when more than half of the world will shift to IPv6.

Why are people still buying and selling IPv4s?

Initially, companies and institutions who bought IPv4s were generously sold IPv4 blocks, and out of these sold blocks there may be just around 16 million IPs left according to RIPE’s database. So what does this mean? This means that there are unallocated IPs still left from the huge blocks sold in the past. This has prompted these companies with excess IPv4s or all of their IPv4s to sell them on the IPv4 marketplace and turn their IPv4 assets into a way to generate revenue for their business. A perfect example is the Massachusetts Institute of Technology (MIT) which sold nearly 8 million IPv4s to Amazon and used the profits to support the organization with the new IPv6 technology.

Read also: Generate revenue from IPv4

What will happen to your company or business if you do not upgrade to IPv6?

If you do not shift right now to IPv6, your business will suffer in the long run, since your competitors and even your customers will have already moved onto IPv6, your ability to stay connected with customers spread out worldwide will suffer, so it is the right time to know more about IPv6 and sell your IPv4s.

Still thinking what is right for your business, freely speak to IPv4.deal experts to know how to know more about transitioning from IPv4 to IPv6.


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