An Introduction to IPv6

May 4, 2020 · by Erik Nygren ·

Background on IPv6

With Internet growth exceeding the limited number of IPv4 addresses, many ISPs and service providers have broadly deployed IPv6. Hosts available over both IPv6 and IPv4 are known as dual stacked. Akamai recommends that sites be enabled with IPv6 wherever possible, both for performance and scale. 

For some countries with extensive IPv6 deployment (including the U.S. and India), end-user IPv6 adoption is established enough that Akamai regularly sees over half of traffic to dual-stacked hosts delivered over IPv6. The actual percentage of IPv6 traffic seen for a given site will vary widely based on the end-user and device population, but many global sites deliver 20-45% of their traffic over IPv6 (in 2019).

We also see that IPv6 typically gets delivered with higher throughput than IPv4. One reason for this is that some large network providers — especially mobile networks — are shifting to IPv6-only for end-user connectivity and provide legacy IPv4 connectivity via IPv4-as-a-service over IPv6. This means that IPv6 traffic can reach the Internet directly, while IPv4 traffic needs to go through network address translation (NAT) exit points.

Growth of IPv6 usage (% of requests which are IPv6) from June 2013 to February 2020 for dual-stacked hosts on Akamai for some top global economies.
Note: U.S. Mobile Carriers data starts in 2016.

Background on hostnames

The domain name system (DNS) is used within the Internet to map hostnames to IP addresses. As such, the DNS configuration for a given hostname, together with client/browser/operating system (OS) behavior, will determine whether a given client will request a resource via HTTP(S) over IPv4 or IPv6. 

DNS record types determine whether a hostname resolves to an IPv4 or IPv6 address. A simplified definition of this relationship follows:

  • When the requested DNS record type is A, DNS returns IPv4 addresses

  • When the requested DNS record type is AAAA, DNS returns IPv6 addresses

A dual-stacked hostname will have both A and AAAA records, returning both IPv4 and IPv6 addresses. Dual-stacked clients will look up both record types. Clients prefer either IPv4 or IPv6 depending on client-specific behaviors, which vary by browser and OS. Today, when dual-stacked clients look up AAAA records for IPv4-only sites, they receive a “no answer” response — when this happens, the dual-stacked clients use the IPv4 addresses from the A record.

An Edge hostname is the integration point between your site’s hostname and the Akamai system that allows your site to be delivered by the Edge Network. Edge hostnames are DNS domains authoritatively owned by us and provide a DNS name for all sites that resolve to an Akamai domain. 

For example, a site in your DNS “” would point (via a CNAME alias) to the Edge hostname “” and resolves its Edge hostname to the individual servers on the Edge network. As a result, the configuration of this Edge hostname controls any behaviors that are determined through a DNS name to IP address assignment, including which IP versions are handed out when assigning end users to Edge servers. 

Most Akamai Edge hostnames use one of the following domains:


You can use the host tool on Linux and OS X to see what a hostname resolves to, including which Edge hostnames are in use. For example, “” has the Edge hostname “”:

$ host is an alias for is an alias for has address has IPv6 address 2600:1401:4000:59f::6a3 has IPv6 address 2600:1401:4000:588::6a3

IPv6 support 

Akamai’s web performance, web security, and media delivery products default to IPv6+IPv4 dual-stacked for new Edge hostnames and property configurations (including for Ion, Dynamic Site Accelerator, Adaptive Media Delivery, and Download Delivery).  For existing Edge hostnames, see the companion blog post on how to Enable IPv6 for Your Edge Hostnames.

Most Akamai products and features have IPv6 support. Below is a partial list:

HD streaming

For legacy media services and HD streaming hostnames, you will need to work with your account team to enable IPv6 (or switch to using another product such as AMD with a different hostname). Hostnames that require account team involvement to dual stack include “*-{i,lh,vh,f,s}” in them.  However, most “*” Edge hostnames CNAME to “*” can be dual stacked using the Edge hostname UI or API.

Edge IP binding

Edge IP binding hostnames are dual stacked by default. If initially configured as IPv4-only, they can be switched to dual stack within the Edge IP binding interface, but cannot be switched back to IPv4-only.


The current default for ChinaCDN is IPv4-only within China. This will change at some point in the future as more IPv6 connectivity becomes available. In the interim, please contact your account team to dual stack in-China delivery.

IPv6 to origin

There is not yet a self-service way to enable contacting origin servers over IPv6. Ask your account team to find out if you may be eligible for a Tech Preview of this functionality.

Storage uploads via HTTPS API

If you have a storage HTTP API upload hostname such as “”, replace “nsu” with “nsu6” to enable IPv6, for example: “” (most other storage upload interfaces do not yet have IPv6 support — contact your account team for details).

IP acceleration

To enable IPv6 with IP acceleration, set the Client IP version to “IPv4 and IPv6 (Dual)” under Edge/Gateway Mapping when creating a slot. If you wish to enable IPv6 for an existing slot, contact your account team.


DNS traffic management / Global Traffic Manager (GTM)

To use IPv6 with GTM, create an IP Version Selector property that references an IPv4 property (which returns A records) and an IPv6 property (which returns AAAA records).

Akamai Control Center and APIs

Akamai Control Center and APIs should all be dual stacked and can be accessed by clients and browsers with IPv6 connectivity.

Authoritative DNS (Fast DNS)

Most Akamai DNS authorities are dual stacked with no further action needed. Zone transfers can also be performed from your master over IPv6.

Learn more

Learn how to enable IPv6 in the second part of our IPv6 series.