Comment 27 for bug 1867375

eoan:

root@lp1867375-e:/etc/systemd/network# cat 10.network
[Match]
Name=eth0

[Network]
DHCP=ipv4
LinkLocalAddressing=ipv6

[DHCP]
RouteMetric=100
UseMTU=true
UseRoutes=false
UseGateway=true

root@lp1867375-e:/etc/systemd/network# dpkg -l systemd|grep systemd
ii systemd 242-7ubuntu3.8 amd64 system and service manager
root@lp1867375-e:/etc/systemd/network# systemctl restart systemd-networkd
root@lp1867375-e:/etc/systemd/network# ip a show eth0
41: eth0@if42: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
    link/ether 00:16:3e:d7:53:48 brd ff:ff:ff:ff:ff:ff link-netnsid 0
    inet 10.202.51.129/24 brd 10.202.51.255 scope global dynamic eth0
       valid_lft 3598sec preferred_lft 3598sec
    inet6 fe80::216:3eff:fed7:5348/64 scope link
       valid_lft forever preferred_lft forever
root@lp1867375-e:/etc/systemd/network# ip r
10.202.51.0/24 dev eth0 proto kernel scope link src 10.202.51.129

root@lp1867375-e:/etc/systemd/network# dpkg -l systemd|grep systemd
ii systemd 242-7ubuntu3.9 amd64 system and service manager
root@lp1867375-e:/etc/systemd/network# systemctl restart systemd-networkd
root@lp1867375-e:/etc/systemd/network# ip a show eth0
41: eth0@if42: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
    link/ether 00:16:3e:d7:53:48 brd ff:ff:ff:ff:ff:ff link-netnsid 0
    inet 10.202.51.129/24 brd 10.202.51.255 scope global dynamic eth0
       valid_lft 3598sec preferred_lft 3598sec
    inet6 fe80::216:3eff:fed7:5348/64 scope link
       valid_lft forever preferred_lft forever
root@lp1867375-e:/etc/systemd/network# ip r
default via 10.202.51.1 dev eth0 proto dhcp src 10.202.51.129 metric 100
10.202.51.0/24 dev eth0 proto kernel scope link src 10.202.51.129
10.202.51.1 dev eth0 proto dhcp scope link src 10.202.51.129 metric 100

and to verify UseRoutes still works:

root@lp1867375-e:/etc/systemd/network# cat 10.network
[Match]
Name=eth0

[Network]
DHCP=ipv4
LinkLocalAddressing=ipv6

[DHCP]
RouteMetric=100
UseMTU=true
UseRoutes=false
#UseGateway=true

root@lp1867375-e:/etc/systemd/network# systemctl restart systemd-networkd
root@lp1867375-e:/etc/systemd/network# ip r
10.202.51.0/24 dev eth0 proto kernel scope link src 10.202.51.129