systemd-networkd: IPv6 prefix delegation disabled by ipv6forwarding=true

[Barry Scott <barry@xxxxxxxxxxxxxxxx>]

I'm building a router for my home using Fedora server as the base.

I have a ISP that provides me with a IPv4 and Ipv6 over PPPoE.

The IPv6 is a /48.

I have the IPv4 all working well.

But the IPv6 configuration I cannot figure out.

I have two interface named internal and external.

In /etc/systemd/network/ppp0-if.network
[Match]
Name=ppp0

[Network]
Description=external network
Address=2001x:x::x::1
IPForward=ipv6

In /etc/systemd/network/internal-if.network
[Match]
Name=internal

[Network]
Description=internal network
Address=172.17.1.1/24
IPForward=ipv6
DNS=127.0.0.1

IPv6SendRA=true
DHCPPrefixDelegation=true

In /etc/systemd/networkd.conf.d/10-forwarding.conf
[Network]
IPv4Forwarding=true

With this config I see prefix delegation to clients but no forwarding.

If I change 10-forwarding.conf to this:

In /etc/systemd/networkd.conf.d/10-forwarding.conf
[Network]
IPv4Forwarding=true
Ipv6Forwarding=true

This sets net.ipv6.conf.all.forwarding = 1 but, prefix delegation is broken.

If I remove Ipv6Forwarding=true and then set net.ipv6.conf.all.forwarding = 1 mnaually forwarding works.

What is the correct way to turn on IPv6Forwarding and still have prefix delegation working?

Barry