Based on my experiments with IPv6 prefix delegation and subnetting I determined a prefix to delegate to Steve. Steve has asked for a /64 delegation like the one I would get from him. The prefix became 1011, derived in this manner: My LAN (0019) is actually subnet 0 in the first level (/56), subnet 1 in the next level (/60) and subnet 9 in the third level (/64). So the 1011 is subnet 10 (first level), 1 second level and again 1 third level. The initial 10 could also be interpreted as subnet 1 in a /52 allocation and subnet 0 in the /56 allocation giving a total of four possible subnet levels.

i) on the VPN router

  ip addr add dev br-lan 2a06:4000:8073:1011::2/64
  ip route add default from 2a06:4000:8073:1011::/64 dev tun2 metric 10    ===> for return traffic

ii) on Ictoan

  ip addr add br-lan 2a06:4000:8073:1011:202:12:89:12/64
  ip route add default from 2a06:4000:8073:1011::/64 via 2a06:4000:8073:1011::2  ===> for return traffic

a) on Vultrgate

  ip route add 2a06:4000:8073:1011::/64 via tun0
  ip route add 2001:44b8:5135:7c07::/64 dev wg0
  Add 2001:44b8:5135:7c07::/64 to Bent's peer "allowed-ips"

The basic IP commands are:

    ip addr add dev eth0 2001:44b8:5135:7c07::44/64
    ip route add default from 2001:44b8:5135:7c07::/64 dev wg0  metric 10    ===> for return traffic
    ip -6 route add 2a06:4000:8073:1011::/64 dev wg0 

Two of the three commands are easily trabsferred to Networkd configurations files but the one with 'default from' isn't. The solution chosed was to write as systemd service file. This file a listed further down. Here is the configuration file for eth0:

#/etc/systemd/network/eth0.network
[Match]
Name=eth0

[Network]
Address=192.168.19.44/24
DNS=192.168.19.5
IPForward=yes
Address=2a06:4000:8073:19::44/64
Address=2001:44b8:5135:7c07::44/64
IPv6AcceptRA=yes

and for the tunnel interface (wg0)

#/etc/systemd/network/wg0.network
[Match]
Name=wg0

[Network]
Address=10.8.3.2/24
IPForward=yes

[Route]
#Gateway=10.8.3.1
Destination=2a06:4000:8073:1011::/6

    ip addr add dev enp2s0 2001:44b8:5135:7c07::5/64
    ip route add default from 2001:44b8:5135:7c07::/64 via 2001:44b8:5135:7c07::44 metric 10  ==> return traffic

IP numbers and device have been updated. Some firewall additions may be required….. Does this all seem right?????

Steve