How to disable IPv6 on Windows Subsystem for Linux?

I tried to disable IPv6 by adding in /etc/sysctl.conf:

net.ipv6.conf.all.disable_ipv6 = 1
net.ipv6.conf.default.disable_ipv6 = 1
net.ipv6.conf.lo.disable_ipv6 = 1

and then running sudo sysctl -p to reload the /etc/sysctl.conf settings - but that threw the error:

sysctl: cannot stat /proc/sys/net/ipv6/conf/all/disable_ipv6: No such file or directory

I tried to also disable it by changing grub configuration /etc/default/grub.d/50-cloudimg-settings.cfg to:

GRUB_CMDLINE_LINUX_DEFAULT="ipv6.disable=1 console=tty1 console=ttyS0"

and then run sudo update-grub but there is no update-grub installed:

sudo: update-grub: command not found

So I am not sure if it is even possible to update grub, but the fact there is a specific configuration located there makes me thing there is.

WSL version:

Description:    Ubuntu 16.04.2 LTS
Release:        16.04
Codename:       xenial

Solution 1:

Instead of disabling IPv6 completely, you can instruct Ubuntu to prefer IPv4 connections to IPv6 by editing the precedence blocks in /etc/gai.conf.

Using this solution:

• You may access servers in Internet with IPv4 an IPv6 servers through a NAT or a router that only understand IPv4
• Use IPv4 and IPv6 in the local network
• Avoid errors, for instance, installing gem files from rubygems.org

Preferring IPv4 over IPV6 addresses

Modifying the precedences in the gai.conf, every time a program calls getaddrinfo() for resolving host names, Linux will prefer the IPv4 addreses. This is very useful when you try to contact a server with both IPv4 and IPv6 addresses from a machine behind a NAT or a router. In addition, you may use IPv6 locally.

1. Edit the /etc/gai.conf

$ sudo vi /etc/gai.conf

2. Uncomment the last lines. Check that file has the next uncommented lines.

#For sites which prefer IPv4 connections change the last line to
precedence ::ffff:0:0/96 100
...
#    For sites which use site-local IPv4 addresses behind NAT there is
#    the problem that even if IPv4 addresses are preferred they do not
#    have the same scope and are therefore not sorted first.  To change
#    this use only these rules:
#
scopev4 ::ffff:169.254.0.0/112  2
scopev4 ::ffff:127.0.0.0/104    2
scopev4 ::ffff:0.0.0.0/96       14

Solution 2:

I disabled IPv6 in the Windows network adapter properties and that took care of the problem for me. My Ubuntu subsytem started using IPv4 instead.

1. Control Panel > Network and Sharing Center > Change adapter settings
   or Win+R ncpa.cpl Enter
2. On your adapter (e.g. Ethernet), right-click > Properties
   or double-click > Properties
   or Alt+Enter
   or Change settings of this connection
3. Uncheck Internet Protocol Version 6 (TCP/IPv6)
4. OK
5. Repeat as necessary for other adapters, like WiFi

Note that this will disable IPv6 for all of Windows (when using that adapter), not just WSL.