Disabling IPv4 and use only IPv6 in Ubuntu

Question

I'm doing some IPv6 related testing, and I wanted to fully disable my IPv4 for the tests on Linux, but couldn't find any easy place to do this. How do I make my IPv6 the only active one?

Answer 1

If you are using Network Manager, click on in and select 'Edit Connections'. Then edit the default connection (or the one you are using) and look under the 'IPv4 Settings' tab. There should be a dropdown for method where you can select 'Disabled'.

Remember to activate it when you're finished testing.

If you're not using Network Manager, ip address del <address>/<netmask> dev <device> should do the trick. For example: ip address del 10.0.0.2/24 dev eth0.

Answer 2

I believe if you edit the /etc/modprobe.d/aliases file and change the following it should work:

alias net-pf-2 ipv4

to:

alias net-pf-2 off

Answer 3

imho the best way to do this is to simply not configure an IPv4 address. Additionally you can choose to disable arp:

ip addr del <ipv4 address>/CIDR dev ethN
(operational example: "ip addr del 192.168.0.1/24 dev eth0")
ip link set dev eth0 arp off

I do this on some boxes that should be only reachable via IPv6 for administative purposes (ssh) - boxes that should not be using the routable Internet for anything else. One such example is a database server that uses an IPv6 ULA via OpenVPN so that only internal hosts can connect to it.