Adding IPv6 to Ubuntu systems

Use this procedure to bind IPv6 IP addresses to your Ubuntu server.

Edit your /etc/network/interfaces file and add the following lines to the end of the file.
```
#IPV6 configuration
iface eth1 inet6 static
pre-up modprobe ipv6 
address 2607:f0d0:2001:0000:0000:0000:0000:0010
netmask 64
gateway 2607:f0d0:2001:0000:0000:0000:0000:0001
```
- The first line defines the interface on which the system uses IPv6.
- The second line loads the module for IPv6.
- The third line identifies the IPv6 address.
- The fourth line defines the netmask for the IPv6 subnet.
- The fifth line defines the default gateway for the IPv6 subnet.
Restart networking with the following command:
```
/etc/init.d/networking restart
```

Verifying IPv6 connectivity

Verify that IPv6 IP is bound

root@server:~# ip -6 address show eth1
3: eth1: mtu 1500 qlen 1000
    inet6 2607:f0d0:2001::/64 scope global
       valid_lft forever preferred_lft forever
    inet6 fe80::230:48ff:fe7e:330a/64 scope link
       valid_lft forever preferred_lft forever
root@server:~#

IPv6 neighbor cache

root@server:~# ip -6 neighbor show dev eth1
2607:f0d0:2001::1 lladdr 00:1b:0d:e6:57:c0 router REACHABLE
root@server:~#

If the neighbor cache shows a fe80 entry, one of the following conditions can apply:

The gateway is not set
The IP is not bound to the correct interface
The IP is not bound correctly to the public interface
The software firewall is blocking IPv6 ICMP.

IPv6 default gateway

root@server:~# ip -6 route show dev eth1
2607:f0d0:2001::/64  proto kernel  metric 256  mtu 1500 advmss 1440 hoplimit 4294967295
fe80::/64  proto kernel  metric 256  mtu 1500 advmss 1440 hoplimit 4294967295
default via 2607:f0d0:2001::1  metric 1024  mtu 1500 advmss 1440 hoplimit 4294967295
root@server:~#

If the default gateway is not listed, you can use the ping6 command to find your default gateway then add it manually using this IP command:

root@server:~# ip -6 route add default via 2607:f0d0:2001::1
root@server:~#