IPv4 vs. IPv6: What is the Difference?


Adoption of IPv6 Addresses Need Not Disrupt Business 

Recently, Verizon shocked its customers by announcing it was out of IPv4 addresses; starting in July, all public IP requests on their wireless network will be filled with IPv6 addresses.

This was the latest announcement in a series of events that have brought IPv6 to the forefront of conversation in the networking world. In 2014, the Internet Corporation for Assigned Names and Numbers (ICANN) announced it was allocating the remaining blocks of IPv4 addresses it had recovered, causing another panic over IP addressing. Prior to that, in 2011, the Internet Assigned Number Authority (IANA) assigned the last two blocks of IPv4 addresses from the free pool.

Verizon titled its announcement “IP Addresses are Getting an Upgrade,” a sentiment that Cradlepoint shares. The move to IPv6 is an opportunity for companies to expand their networks, enhance their capabilities, and simplify their designs. Adopting IPv6 is an exercise that should be embraced, not feared. Given the advantages of IPv6 and its inevitable proliferation, IT teams should act now, looking for ways to integrate IPv6 into future network designs.

Much of the anxiety and confusion related to the transition to IPv6 stems from a lack of understanding of how the protocols differ. There are a few key differences to understand.


The first difference is size — both the size of the address itself, and the number of addresses available in each standard. IPv4 is a 32-bit address, meaning it has 2^32nd power (or roughly 4.2 billion) addresses. IPv6, on the other hand, has 2^128 (or approximately 340 undecillion) addresses. To give an idea of scale, IPv4 would allow for a little more than half the world’s population to each have a unique IP address. With IPv6, we can "... assign an IP address to every atom on the surface of the Earth, and still have enough addresses left to do another 100+ earths.

In simpler terms, this protocol should last us a while.


Another advantage is the efficiency of the IPv6 header. The IPv4 header included a lot of fields that were required but not always needed. This complexity caused processing delays in routing, as each device operating at OSI layer 3 and higher had to process each field to forward the IP packet correctly.

The IPv6 standard simplifies the header by eliminating the unneeded fields and creating a process for extending the header optionally. As the diagram below demonstrates, the IPv6 header is bigger than IPv4 (20 bytes vs. 40 bytes), but the format is much simpler. This combination of factors allows an IPv6 packet to be processed and forwarded much faster.

Address Assignment

An important aspect of IPv6 is how addresses are assigned to devices. Many people who are wary of IPv6 are nervous about what they perceive as a potentially more complex IP assignment process due to the longer address.

In the world of IPv4, we must assign IP addresses to network nodes or rely on DHCP to handle the dynamic assignment. DHCP requires a network resource to maintain a database of IP addresses and respond to requests from clients for address assignment. IPv6, however, includes a process called Stateless Address Auto-Configuration (SLAAC). This process allows devices to configure their own IP address by combining prefix information collected from router advertisement with its own MAC address to create a unique host IP address. (Note that DHCP will not disappear with IPv6, and DHCPv6 was designed to work with IPv6). This is a clear advantage to IPv6 and a reason to embrace adoption.

Get Ready for IPv6

Are you ready for IPv6? Most likely you already are using it and didn’t even realize it, because LTE carriers have been utilizing IPv6 for several years. 

Cradlepoint is also ready to help our customers adopt IPv6. Cradlepoint’s router OS supports all major features needed to be compatible with IPv6, including prefix delegation (both wireline and LTE), DHCPv6, and SLAAC. All of this functionality is enabled by a simple user interface, making IPv6 that much easier to deploy. So, why are you waiting?

Configure Your Router to Use IPv6

To learn how to configure a Cradlepoint router to use IPv6, read this KnowledgeBase article.



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