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World IPv6 Day and how to add IPv6 support to a web server

Today, 6th of June we celebrate World IPv6 day. Ipv6 is the new standard for IP protocols. IPv6 is important because, as everyone by now should know, the public IPv4 address space is running out. In fact all IPv4 address blocks have already been mostly consumed by registrars and the resource problem is being avoided by recycling old addresses and using NAT-techniques, which cause problems for many VoIP and P2P services. IPv6 also offers better network security (IPsec) built in.


We already wrote about taking IPv6 in use on a workstation earlier. Now we’ll explain how to add it to a web server.

Note, we are deliberately not using old school commands (ifconfig, route, netstat) below, but instead the modern versions (ip and ss). It is time to move on with modern utilities too.

First you need to add a IPv6 address to your network interface. On a Linux server to add a static address edit the file /etc/network/interfaces like this:

auto lo
iface lo inet loopback

auto eth0
iface eth0 inet static
 # dns-* options are implemented by the resolvconf package, if installed

iface eth0 inet6 static
 address 2a00:14c0:1:307:aa51::158
 netmask 64
 gateway 2a00:14c0:1:307::1

The restart the network so that changes take effect:

$ sudo /etc/init.d/networking restart

The interface configuration should show something in the lines of:

$ ip addr show eth0
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
 link/ether 52:54:00:87:05:3c brd ff:ff:ff:ff:ff:ff
 inet brd scope global eth0
 inet6 2a00:14c0:1:307:aa51::158/64 scope global 
 inet6 fe80::5054:ff:fe87:53c/64 scope link 

You may test from another machine running:

$ ping6 2a00:14c0:1:307:aa51::158

You can verify that the routes are sensible using using the -6 option:

$ ip -6 route
2a00:14c0:1:307::/64 dev eth0 proto kernel metric 256 expires 2592027sec
fe80::/64 dev eth0 proto kernel metric 256 
default via fe80::20c:86ff:fe14:d038 dev eth0 proto kernel metric 1024 expires 1665sec hoplimit 64
default via 2a00:14c0:1:307::1 dev eth0 metric 1024

For route testing you can use the tool traceroute6. To check that the traffic really flows correctly, try logging in remotely using ssh -6.

Domain name records for IPv6

Now open in your browser http://[2a00:14c0:1:307:aa51::158]/ to see if you web server servers anything for the IPv6 address. Alternatively you can use the website if you don’t yet have IPv6 configured on your workstation.

Now when the service has a IPv6 address, you can start advertising it by adding a DNS AAAA record after your normal A record: A AAAA 2a00:14c0:1:307:aa51::158

If you want to be extra cool, add a subdomain ipv6 (e.g., With this address it is very visual to test if IPv6 works or not on any browser anywhere.

Configuring web servers Apache or Nginx

Next you need to configure you web server to listen for port 80 on both IPv4 and IPv6.

In Apache you don’t need to configure anything special, as long as the Listen and NameVirtualHost directives don’t specify an IP-address but just port 80 in a generic way:

NameVirtualHost *:80
Listen 80

For Nginx, add inside the server { } section the following line:

server {
  listen [::]:80 default_server;
  listen [::]:443 default_server ssl;

If you are missing a listen line altogether or it looks like listen 80; it means Nginx was listening only for the IPv4 address port 80.

After the change, restart the server (reload is not enough) with:

$ sudo service nginx reload

Confirm with netstat that there indeed are servers listening:

$ sudo ss -6lp
State Recv-Q Send-Q Local Address:Port Peer Address:Port 
LISTEN 0 128 :::http :::* users:(("nginx",25706,28),("nginx",25705,28),("nginx",1826,28))

You can test the result with:

curl -I -6 -v
* About to connect() to port 80 (#0)
*   Trying 2a00:14c0:1:307:aa51::158... connected
HTTP/1.1 302 Moved Temporarily
Server: nginx

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