Netplan has no option to enable dhcpv6 prefix delegation like ifupdown did

Bug #1771886 reported by Bryce Larson
This bug affects 29 people
Affects Status Importance Assigned to Milestone

Bug Description

When using ifupdown, you can put 'request_prefix 1' in order to specify for dhclient to request an dhcpv6 prefix delegation. I also understand that systemd-networkd also supports this, see If netplan is to fully replace ifupdown feature for feature, it needs to support this functionality as I am using that feature with ifupdown and cannot upgrade to netplan without it.

I understand from the website that you guys want cases like this to be reported here. Let me know if that is not the case or if there is a better place to put things like this.

Revision history for this message
Bryce Larson (bryceml) wrote :

Another thing that relates to this is the ability to specify what the duid is that is sent in the dhcpv6 request. If I recall correctly systemd-networkd offers the ability to specify the duid.

Revision history for this message
Ryan Harper (raharper) wrote :

Hi Bryce,

Thanks for taking the time to report this issue.

netplan doesn't yet support setting dhcpv6 prefix delegation. Thanks for the link.

The relevant networkd sections are available and documented here:


[IPv6PrefixDelegation] Section Options

We'll need to see what, if any support for this there is in NetworkManager and then determine what key/values to use to control and then add support to the backend renders.

W.r.t the DUID, networkd currently sends an RFC4361-compliant Client ID, which is the combination of IAID and DUID; this is generated automatically by systemd. If you need to override this value currently you need to create a global override to /etc/systemd/network.conf, details here.

That's not currently modeled in the yaml or backends either.

Changed in netplan:
status: New → Confirmed
Revision history for this message
Wladimir Mutel (mwg) wrote :

1 year has definitely passed since the release of Ubuntu 18.04
netplan had been updated through 0.36 -> 0.40 -> 0.97 -> 0.98
any progress in supporting dhcp6-pd there ???

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John Ioannidis (ubuytu) wrote :

It's now 2020. I really have to ask: who writes networking software, let alone making it the default, and does not consider fully-supporting IPv6 a requirement?

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John Ioannidis (ubuytu) wrote :

When will this be fixed? Why was netplan made the default when it does not have feature parity with ifupdown? Why is this question being ignored?

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Konstantin Novitsky (novitk) wrote :

Gave up on Ubuntu in a router/network appliance space due to this. Sure, I can remove netplan and use ifupdown, but why bother when openwrt just works!

Revision history for this message
Wladimir Mutel (mwg) wrote :

Fortunately, with systemd-networkd + wpa_supplicant you could go without any of {netplan, ifupdown, NetworkManager} on both modern Ubuntu or modern Debian. As you may imagine, netplan is just a frontend generating ("rendering") configs for one of possible backends within {networkd, NetworkManager}. So you just copy /run/systemd/network/* into /etc/systemd/network/ , after which you may remove all netplan and related packages and go ahead with systemd-networkd only (which, unfortunately, is nailed to the core of modern Linuxes pretty firmly and not that easily detachable).

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David Burrow (dnburrow) wrote :

Would still love to see IPv6-PD implemented in netplan.

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DanyChen (danychen) wrote :

I have this problem too, netplan has so many ancient bugs that are still open, I don't know why ubuntu integrate netplan, why don't make cloud-init just write networkd config files.

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Avamander (avamander) wrote :

Well this is an annoying bug, makes netplan useless for the biggest IPv6 ISP in the country.

tags: added: rookie-mistake
Lukas Märdian (slyon)
tags: added: fr-1731
Changed in netplan:
importance: Undecided → Wishlist
Revision history for this message
Mike Borsetti (mborsetti) wrote :

Ugly workaround until this bug is fixed, but this seems to work with Ubuntu 20.04.3 LTS and 21.04. It's executed at startup, e.g. from rc.local, as root; br0 in this case is the interface to a WAN network so adapt to your system before running.

echo "IPv6SendRA=yes" >> /run/systemd/network/
echo "DHCPv6PrefixDelegation=yes" >> /run/systemd/network/
echo "IPv6PrivacyExtensions=yes" >> /run/systemd/network/
systemctl restart systemd-networkd

Yes, it's ugly and am sure breaks a whole lot of Netplan's goals, but at this point is Netplan that breaks the goal of having a prefix-delegated network so it's a (much) lesser evil IMHO.

Revision history for this message
Lukas Märdian (slyon) wrote :

A more elegant way to implement this workaround would probably be to put that configuration snippet into a drop-in override (as described here, e.g.:

$ cat /etc/systemd/network/

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