IPv6 Prefix Delegation with NetPlan

No. That’s the short of it.

Longer version starts with me setting up my new Ubuntu server and deciding to use netplan to setup network interfaces. Nothing too big. Just a few bonds here and there. And all seemed fine until I tried to setup email and noticed the following message in syslog:

postfix/smtp[49721]: connect to alt1.aspmx.l.google.com[209.85.146.27]:25: Connection timed out
postfix/smtp[49721]: connect to aspmx5.googlemail.com[2607:f8b0:4002:c08::1b]:25: Network is unreachable

Once I double-checked, I noticed syslog was right - I only had link-local address assigned to interface. Ok, so DHCPv6 only turns on DHCP and not prefix delegation I use for my network. Easy-peasy, that’s surely matter of just turning on the correct setting…

Or finding a matching bug. Yep, prefix delegation that’s perfectly valid and well supported IPv6 address allocation method is not supported.

But ticket did solve my problem. As advised, I simply reverted to use networkd (don’t forget to use systemctl enable systemd-networkd).

PS: Here are my networkd files that work with IPv6 PD.

[NetDev]
Name=bond0
MACAddress=00:25:90:ba:31:40
Kind=bond

[Bond]
Mode=802.3ad
LACPTransmitRate=fast
MIIMonitorSec=100ms
TransmitHashPolicy=layer2+3

[Match]
Name=bond0

[DHCP]
RouteMetric=100
UseMTU=true

[Network]
DHCP=yes
IPv6PrefixDelegation=yes
IPv6PrivacyExtensions=true
LinkLocalAddressing=ipv6
ConfigureWithoutCarrier=yes

[Match]
PermanentMACAddress=00:25:90:ba:31:40

[Network]
Bond=lan

[Match]
PermanentMACAddress=00:25:90:ba:31:41

[Network]
Bond=lan