Server 3.x


The VPN server software supports both IPv4 and IPv6. We’ve reached a point in the “evolution” of the Internet that IPv4 NAT is unavoidable, but for IPv6 there is no excuse to not issue proper public IPv6 addresses to the VPN clients.

By default the VPN server installation will also perform NAT for IPv6 traffic and set some less than optimal configuration parameters. This is only meant for testing. For production you SHOULD switch to public IPv6 addresses for your VPN clients!

As already mentioned in other places in the documentation, your VPN server MUST have static IPv4 and IPv6 address configurations!

IPv6 Routing#

IPv6 routing can be, and is, by default enabled in /etc/sysctl.d/70-vpn.conf where eth0 is the external interface of your VPN server:

# **ONLY** needed for IPv6 configuration through auto configuration. Do **NOT**
# use this in production, you SHOULD be using STATIC addresses!
net.ipv6.conf.eth0.accept_ra = 2

# enable IPv4 and IPv6 forwarding
net.ipv4.ip_forward = 1
net.ipv6.conf.all.forwarding = 1

For production you MUST remove the net.ipv6.conf.eth0.accept_ra = 2 line as you’ll be using static IPv6 addresses and thus not need this, so the only contents SHOULD be:

net.ipv4.ip_forward = 1
net.ipv6.conf.all.forwarding = 1

When making changes here, reboot your server to make sure the changes are properly propagated. Test your IPv6 connectivity after reboot.

NOTE: do NOT remove the net.ipv6.conf.all.forwarding = 1 in an attempt to try and disable IPv6. This will lead to (long) timeouts when clients attempt to connect to services that support native IPv6.

Routed IPv6 Prefix#

The easiest, and best way is to have a public IPv6 prefix routed to the public IPv6 address of your VPN server.

See Public Addresses on how to configure public IPv6 addresses in your VPN server as well as the firewall configuration when using public IP addresses.

Disabling IPv6#

If you want to disable IPv6, because your VPN server does not have an IPv6 connection, you can do so as documented here. Technically this does not disable IPv6, but drop the IPv6 packets as soon as possible as to not result in any delays when attempting to services that have native IPv6 support.

IPv6 can currently NOT be fully disabled in the VPN service!