Enabling dualstack connections
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Fastly supports dualstack connections, which allow traffic to your websites and applications to be served over both IPv4 and IPv6. This guide covers enabling IPv6 for connections between your end users and Fastly’s edge network. Connections from Fastly to your origin servers can also use IPv6, which is configured separately in your host settings.
Once enabled, clients connect over whichever protocol is faster. Most modern clients implement Happy Eyeballs, which prefers IPv6 when both protocols perform equally.
Limitations and considerations
Note the following limitations and considerations:
- If you use our Anycast IPv4 addresses for apex domains, contact Fastly support and we’ll provide you with the appropriate Anycast IPv6 addresses.
- Fastly's geolocation features work with IPv6 addresses.
- You can track whether a request came in as an IPv6 request with the
req.is_ipv6VCL variable as well as by the IPv6 format itself when logging%h.
Enabling dualstack
To enable traffic to be served over IPv6 and IPv4 addresses, follow the instructions below appropriate to your CNAME record. If you’re using one of our TLS products, you can find your CNAME records in the HTTPS and network tab, under DNS details. If the name ends in map.fastly.net, it is a customer-specific hostname. Otherwise, it is a Fastly-shared hostname.
Once enabled, test that you can connect over IPv6.
Enabling dualstack for Fastly-shared hostnames
You can enable IPv6 dualstack (IPv4 and IPv6) functionality for your hostname by prefixing your CNAME record with dualstack. For example, if you have traffic on an IP address pool nicknamed j.sni (which supports a minimum TLS version of 1.2, a maximum TLS version of 1.3, does not support 0RTT, and offers HTTP/2), then you could use the following dualstack options:
dualstack.j.sni.global.fastly.net(dualstack global map)dualstack.j.sni.us-eu.fastly.net(dualstack NA/EU)
If you are using m.ssl (which supports a minimum and maximum TLS version of 1.2 and HTTP/1.x only), then you could use the following dualstack options:
dualstack.m.ssl.global.fastly.net(dualstack global map)dualstack.m.ssl.us-eu.fastly.net(dualstack NA/EU)
HINT: For more information on updating your CNAME record, see our instructions on updating your CNAME record with your DNS provider.
Enabling dualstack on customer-specific hostnames
If you have a customer-specific hostname, contact support and we'll provide you with a parallel IPv6 map or enable dualstack on your current one. By default, maps will be HTTP/2 enabled and have a global billing region set. Be sure to specify any required changes when having a new map created.
Testing IPv6
Once you’re up and running with IPv6, test IPv6 by entering a dig command in a terminal application to make sure your map returns AAAA records. For example, you can type something similar to this:
$ dig www.example.com AAAA +shortwhere www.example.com is the domain that you’re testing.
Your output should appear similar to the following:
2606:2800:220:1:248:1893:25c8:1946
You can also use a tool like What's my DNS and choose the AAAA option to see how clients around the world are resolving to your CNAME record.
