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Table of contents
Temporarily Assigning Multiple Individual IPv6 Addresses for Testing
Temporarily Making the Server Reachable for All IPs in the Subnet
Permanently Assigning Individual Single IPv6 Addresses (Reboot Safe)
Setting up IPv6 DNS AAAA Records in the Hetzner DNS Management WebUI
Generating a Letsencrypt Certificate for an IPv6 / AAAA Domain
Configuring the Nginx Webserver for Listening on IPv6 Addresses
Configuring the Apache2 Webserver for Listening on IPv6 Addresses
Introduction
Before starting with IPv6 you should check if your Internet Service Provider (ISP) supports IPv6. You can do so by simply accessing ipv6.google.com. This is the google search page, but via IPv6 instead of IPv4. If this works for you, you can continue reading the article. If it does not, complain to your ISP to setup IPv6 or start using a VPN like mullvad.net, which will allow you to access IPv6.
At the time of this writing (April 2024), about half the internet supports IPv6, with France and Germany having the best coverage at about 75%, the US only has about 45%.
For hosting public websites, these aren't exactly shining numbers, but for hosting websites behind Content Delivery Networks (CDN) like cloudflare, this is irrelevant, as cloudflare supports IPv6 and can access your backend webserver at its IPv6 address.
At Blunix, we also like to exclusively assign IPv6 addresses to servers that are not meant to be publicly accessible, but only via an internal company VPN. For these company-internally used servers we use a (cost-free) IPv6 address for administrative purposes, with all WebUIs and other services only being accessible over the company internal VPN.
Creating a Hetzner Cloud Server with an IPv6 Address
Create a new server and make sure IPv6 is enabled. You can select to only use an IPv6 address for your server to save a bit of money. For this blog post, we selected to not assign an IPv4 address to the server. Pretty much all modern computers and mobile devices understand IPv6 by now, so you don't really need an IPv4 address anymore.
After creating the cloud or physical server, the Hetzner Cloud WebUI shows you the IPv6 subnet that was assigned to the server. At the time of this writing, each server is assigned a /64 subnet. Fun fact: a /64 IPv6 subnet contains 18.45 quintillion, or 18.446.744.073.709.551.616, or 18.45 * 10^18 usable IPv6 addresses. This should be enough to host a couple of websites. Refer to the ripe net documentation on understanding IP addressing and CIDR charts for additional information.
Connecting to the Hetzner Cloud Server via SSH by using its IPv6 Address
If your subnet is 2a01:4f8:1c1c:dd6::/64, then you can connect to the Hetzner Cloud server via SSH by adding a 1 at the end:
ssh root@2a01:4f8:1c1c:dd6::1
The authenticity of host '2a01:4f8:1c1c:dd6::1 (2a01:4f8:1c1c:dd6::1)' can't be established.
ED25519 key fingerprint is SHA256:WBp/Jd5omTEuFOKI6tRfV5AwtBd9y+iS0de1cRr88B8.
This key is not known by any other names
Are you sure you want to continue connecting (yes/no/[fingerprint])? yes
Warning: Permanently added '2a01:4f8:1c1c:dd6::1' (ED25519) to the list of known hosts.
Linux ipv6-blogpost 6.1.0-18-amd64 #1 SMP PREEMPT_DYNAMIC Debian 6.1.76-1 (2024-02-01) x86_64
The programs included with the Debian GNU/Linux system are free software;
the exact distribution terms for each program are described in the
individual files in /usr/share/doc/*/copyright.
Debian GNU/Linux comes with ABSOLUTELY NO WARRANTY, to the extent
permitted by applicable law.
root@ipv6-blogpost:~#
Assigning additional IPv6 addresses
Lets configure the network interface to be reachable on more than one IPv6 address.Temporarily Assigning IPv6 Addresses for Testing
To quickly add a new IPv6 address to your server, use the following command:
ip address add 2a01:4f8:1c1c:dd6::3 dev eth0
To check if this is working, run the following command from your workstation:
ping6 2a01:4f8:1c1c:dd6::3
You can choose any address between the minimum and maximum value in the assigned subnet. Remember that IPv6 addresses are written hexadecimal values: "0-9" and "a-f".
Lowest possible address: 2a01:4f8:1c1c:dd6:0000:0000:0000:0000
Largest possible address: 2a01:4f8:1c1c:dd6:ffff:ffff:ffff:ffff
More examples:
ip address add 2a01:4f8:1c1c:dd6:0000:0000:0000:1000 dev eth0
ip address add 2a01:4f8:1c1c:dd6:0000:0000:0815:0000 dev eth0
ip address add 2a01:4f8:1c1c:dd6:af9c:1c59:91a5:1d63 dev eth0
If you only use ip address add, the configuration will be lost after the next reboot. Refer to the next section on how to make those configurations reboot safe.
Temporarily Making the Server Reachable for All IPs in the Subnet
You can also make the server listen to every IP address in the whole /64 subnet like this:
ip route add local 2a01:4f8:1c1c:dd6::/64 dev eth0
Permanently Assigning Individual Single IPv6 Addresses (Reboot Safe)
The IPv6 address that your server was accessible for after its creation is configured in /etc/network/interfaces.d/50-cloud-init:
cat /etc/network/interfaces.d/50-cloud-init
# This file is generated from information provided by the datasource. Changes
# to it will not persist across an instance reboot. To disable cloud-init's
# network configuration capabilities, write a file
# /etc/cloud/cloud.cfg.d/99-disable-network-config.cfg with the following:
# network: {config: disabled}
auto lo
iface lo inet loopback
auto eth0
iface eth0 inet dhcp
# control-alias eth0
iface eth0 inet6 static
address 2a01:4f8:1c1c:dd6::1/64
dns-nameservers 2a01:4ff:ff00::add:1 2a01:4ff:ff00::add:2
gateway fe80::1
Copy the relevant section and create a new file /etc/network/interfaces.d/99-custom. Add a configuration block like this for each IPv6 address you want the server to be reachable at. Note that if you configure a whole subnet, the server will not be reachable for all IPs in the subnet - the block above will only make the server reachable at 2a01:4f8:1c1c:dd6::1, not at every IP in 2a01:4f8:1c1c:dd6::1/64! Refer to this serverfault.com thread for additional information.
Remember that the normalized version of 2a01:4f8:1c1c:dd6::1 is 2A01:04F8:1C1C:0DD6:0000:0000:0000:0001, and that specifying a /128 subnet in IPv6 is like specifying a /32 subnet in IPv4 - it refers to a single IP address.
cat /etc/network/interfaces.d/99-custom
# app1.blunix.com
iface eth0 inet6 static
address 2a01:4f8:1c1c:dd6:ffff:ffff:ffff:fff0/128
dns-nameservers 2a01:4ff:ff00::add:1 2a01:4ff:ff00::add:2
gateway fe80::1
# app2.blunix.com
iface eth0 inet6 static
address 2a01:4f8:1c1c:dd6:1234:5678:90ab:cdef/128
dns-nameservers 2a01:4ff:ff00::add:1 2a01:4ff:ff00::add:2
gateway fe80::1
To apply changes to configuration files below /etc/network/interfaces.d/ execute the following command. This will restart your servers network and the server will be unreachable for about two to three seconds. In this time your SSH session will hang, which is normal.
systemctl restart networking
Permanently Assigning a whole IPv6 Subnet (Reboot Safe)
To create a reboot safe configuration for making the server reachable at all IPs in the subnet, simply add the route commands at the bottom:
cat /etc/network/interfaces.d/99-custom
# Reachable for all IPs in the /64
iface eth0 inet6 static
address 2a01:4f8:1c1c:dd6::1/64
dns-nameservers 2a01:4ff:ff00::add:1 2a01:4ff:ff00::add:2
gateway fe80::1
# Setup to respond to any address in the subnet
post-up ip -6 route add local 2a01:4f8:1c1c:dd6::1/64 dev eth0
pre-down ip -6 route del local 2a01:4f8:1c1c:dd6::1/64 dev eth0
Setting up IPv6 DNS AAAA Records in the Hetzner DNS Management WebUI
For each IPv6 address you want to use for hosting a website, or any other service for that matter, configure one AAAA type DNS records. In Hetzners DNS Management WebUI, this can be done like this:
To verify that you setup the DNS record correctly you can simply ping the new domain. Make sure to use ping6 instead of ping:
ping6 -c 3 ipv6-blogpost.blunix.com
PING ipv6-blogpost.blunix.com(ipv6-blogpost.blunix.com (2a01:4f8:1c1c:dd6:1234:5678:90ab:cdef)) 56 data bytes
64 bytes from ipv6-blogpost.blunix.com (2a01:4f8:1c1c:dd6:1234:5678:90ab:cdef): icmp_seq=1 ttl=52 time=106 ms
64 bytes from ipv6-blogpost.blunix.com (2a01:4f8:1c1c:dd6:1234:5678:90ab:cdef): icmp_seq=2 ttl=52 time=206 ms
64 bytes from ipv6-blogpost.blunix.com (2a01:4f8:1c1c:dd6:1234:5678:90ab:cdef): icmp_seq=3 ttl=52 time=125 ms
Setting up IPv6 records in /etc/hosts
You can also setup /etc/hosts records for IPv6 addresses using the exact same way you would setup IPv4 records:
cat << EOF | sudo tee -a /etc/hosts
2a01:4f8:1c1c:dd6:1234:5678:90ab:cdef ipv6-blogpost.blunix.com
Generating a Letsencrypt Certificate for an IPv6 / AAAA Domain
There is nothing special to generating Letsencrypt certificates for IPv6 domains. In the following example we automatically agree to the terms of service (--agree-tos), spin up a standalone webserver (--standalone) and refuse to provide an email address, which only means that we will not be notified by email two weeks before the domain expires (--register-unsafely-without-email).
certbot certonly --agree-tos --standalone --register-unsafely-without-email --domain ipv6-blogpost.blunix.com
Saving debug log to /var/log/letsencrypt/letsencrypt.log
Account registered.
Requesting a certificate for ipv6-blogpost.blunix.com
Successfully received certificate.
Certificate is saved at: /etc/letsencrypt/live/ipv6-blogpost.blunix.com/fullchain.pem
Key is saved at: /etc/letsencrypt/live/ipv6-blogpost.blunix.com/privkey.pem
This certificate expires on 2024-07-23.
These files will be updated when the certificate renews.
Certbot has set up a scheduled task to automatically renew this certificate in the background.
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If you like Certbot, please consider supporting our work by:
* Donating to ISRG / Let's Encrypt: https://letsencrypt.org/donate
* Donating to EFF: https://eff.org/donate-le
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Configuring the Nginx Webserver for Listening on IPv6 Addresses
The following example nginx vhost is configured to serve SSL for all of the 18.45 quintillion IPv6 addresses. Keep in mind that we have to create AAAA DNS Records for each IP, as well as configure them in /etc/network/interfaces.d/ as described above for the IP to work.
The following SSL configuration is only an example - to create a proper configuration, take a look at the mozilla SSL configuration generator for webservers. The following commands let you determine your nginx and openssl version:
nginx -v
nginx version: nginx/1.22.1
openssl version
OpenSSL 3.0.11 19 Sep 2023 (Library: OpenSSL 3.0.11 19 Sep 2023)
Here is the nginx vhost configuration for hosting a website using an IPv6 address on Hetzner Cloud. Notice the two listen directives, one for localhost (127.0.0.1) and one for one or all possible IPv6 addresses:
server {
server_name ipv6-blogpost.blunix.com;
listen 127.0.0.1:80;
listen [::]:80;
return 301 https://ipv6-blogpost.blunix.com$request_uri;
}
server {
server_name ipv6-blogpost.blunix.com;
listen 127.0.0.1:443 ssl http2;
listen [::]:443 ssl http2;
root /var/www/html;
index index.html index.htm index.nginx-debian.html;
location / {
try_files $uri $uri/ =404;
}
ssl_certificate /etc/letsencrypt/live/ipv6-blogpost.blunix.com/fullchain.pem;
ssl_certificate_key /etc/letsencrypt/live/ipv6-blogpost.blunix.com/privkey.pem;
ssl_session_timeout 1d;
ssl_session_cache shared:MozSSL:10m;
ssl_session_tickets off;
# intermediate configuration
ssl_protocols TLSv1.2 TLSv1.3;
ssl_ciphers ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:DHE-RSA-AES128-GCM-SHA256:DHE-RSA-AES256-GCM-SHA384:DHE-RSA-CHACHA20-POLY1305;
ssl_prefer_server_ciphers off;
# HSTS (ngx_http_headers_module is required) (63072000 seconds)
add_header Strict-Transport-Security "max-age=63072000" always;
}
Configure Nginx to Listen on a Single IPv6 Address
To configure Nginx to only listen on a specific IPv6 address simply state the address in brackets:
listen [2a01:4f8:1c1c:dd6:1234:5678:90ab:cdef]:80;
listen [2a01:4f8:1c1c:dd6:1234:5678:90ab:cdef]:443 ssl http2;
Configure Nginx to Listen on Multiple IPv6 Addresses
When using public IP addresses, there is no good usecase for this. Normally, you should only use one public IP per website. However when using a public as well as an internal (private) IP, this can make sense.
In order for nginx to make a vhost available on multiple IP addresses, you can simply specify multiple listen directives to configure one Nginx Vhost to be available on multiple IPv6 addresses:
listen [2a01:4f8:1c1c:dd6:1234:5678:90ab:cdef]:80;
listen [2a01:4f8:1c1c:dd6:0000:0000:0000:1234]:80;
listen [2a01:4f8:1c1c:dd6:1234:5678:90ab:cdef]:443 ssl http2;
listen [2a01:4f8:1c1c:dd6:0000:0000:0000:1234]:443 ssl http2;
Configure Nginx to Listen on an IPv6 Subnet
Nginx does not provide an option to listen on a whole subnet, IPv4 or IPv6. You can configure Nginx to listen on all incoming IPv6 traffic like this:
listen [::]:443 ssl http2;
And then simply use your firewall to allow only the addresses you wish to let through.
Configuring the Apache2 Webserver for Listening on IPv6 Addresses
The following example apache2 vhost is configured to serve SSL for all of the 18.45 quintillion IPv6 addresses. Keep in mind that we have to create AAAA DNS Records for each IP, as well as configure them in /etc/network/interfaces.d/ as described above for the IP to work.
The following SSL configuration is only an example - to create a proper configuration, take a look at the mozilla SSL configuration generator for webservers. The following commands let you determine your apache2 and openssl version:
apache2 -v
Server version: Apache/2.4.59 (Debian)
Server built: 2024-04-05T12:02:26
openssl version
OpenSSL 3.0.11 19 Sep 2023 (Library: OpenSSL 3.0.11 19 Sep 2023)
First enable the apache2 ssl and headers modules:
a2enmod ssl headers
Here is the apache2 vhost configuration for hosting a website using an IPv6 address on Hetzner Cloud. Notice the two listen directives, one for localhost (127.0.0.1) and one for one or all possible IPv6 addresses:
<VirtualHost [::]:80>
ServerName ipv6-blogpost.blunix.com
DocumentRoot /var/www/html
Redirect permanent / https://ipv6-blogpost.blunix.com
</VirtualHost>
<VirtualHost [::]:443>
ServerName ipv6-blogpost.blunix.com
DocumentRoot /var/www/html
SSLEngine on
SSLCertificateFile /etc/letsencrypt/live/ipv6-blogpost.blunix.com/fullchain.pem
SSLCertificateKeyFile /etc/letsencrypt/live/ipv6-blogpost.blunix.com/privkey.pem
Protocols h2 http/1.1
Header always set Strict-Transport-Security "max-age=63072000"
SSLProtocol all -SSLv3 -TLSv1 -TLSv1.1
SSLCipherSuite ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:DHE-RSA-AES128-GCM-SHA256:DHE-RSA-AES256-GCM-SHA384:DHE-RSA-CHACHA20-POLY1305
SSLHonorCipherOrder off
SSLSessionTickets off
</VirtualHost>
Configure Apache2 to Listen on a Single IPv6 Address
To configure Apache2 to only listen on a specific IPv6 address simply state the address in brackets:
listen [2a01:4f8:1c1c:dd6:1234:5678:90ab:cdef]:80;
listen [2a01:4f8:1c1c:dd6:1234:5678:90ab:cdef]:443 ssl http2;
Configure Apache2 to Listen on a Single IPv6 Address
While you can specify multiple IPv4 or IPv6 addresses in /etc/apache2/ports.conf like so:
Listen [2a01:4f8:1c1c:dd6:1234:5678:90ab:0000]:443
Listen [2a01:4f8:1c1c:dd6:1234:5678:90ab:1111]:443
Listen [2a01:4f8:1c1c:dd6:1234:5678:90ab:2222]:443
But you are still limited to one single IP in each VirtualHost configuration:
<VirtualHost [2a01:4f8:1c1c:dd6:1234:5678:90ab:0815]:443>
Which you can set to listen on all possible IPs:
<VirtualHost [::]:443>
From there you have to use the ServerName directive to sort the incoming requests:
ServerName ipv6-blogpost.blunix.com
Configure Apache2 to Listen on an IPv6 Subnet
Apache2 does not provide an option to listen on a whole subnet, neither IPv4 nor IPv6. You can configure Apache2 to listen on all incoming IPv6 traffic like this:
listen [::]:443 ssl http2;
And then simply use your firewall to allow only the addresses you wish to let through.
Checking if the Website is Reachable
Your website should now be configured and reachable over its IPv6 address(es). Time to check if it is working correctly.
Checking the Website using a Browser
Simply enter the URL in your browser:
Testing the Website with Curl
You can also use curl to check if the website is online:
curl -6 --head --location http://ipv6-blogpost.blunix.com
HTTP/1.1 301 Moved Permanently
Server: nginx/1.22.1
Date: Wed, 24 Apr 2024 11:03:53 GMT
Content-Type: text/html
Content-Length: 169
Connection: keep-alive
Location: https://ipv6-blogpost.blunix.com/
HTTP/2 200
server: nginx/1.22.1
date: Wed, 24 Apr 2024 11:03:54 GMT
content-type: text/html
content-length: 615
last-modified: Wed, 24 Apr 2024 09:20:47 GMT
etag: "6628ceef-267"
strict-transport-security: max-age=63072000
accept-ranges: bytes