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Coops
Asked: 2022-04-02 14:46:22 +0800 CST

systemd-networkd not launching DHCPv6 client

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The systemd-networkd documentation makes this statement...

By enabling DHCPv6 support explicitly, the DHCPv6 client will
be started regardless of the presence of routers on the link

This is the behavior I'm looking for - ignoring any RAs which may or may not appear, and just launching a DHCPv6 client.

I see no evidence that networkd is launching a dhcpv6 client, either from the output of SYSTEMD_LOG_LEVEL=debug /lib/systemd/systemd-networkd or from tcpdump.

I can however confirm my DHCPv6 server is working if I manually evoke dhclient.

root@client:~# dhclient -6 -v eth0
[...]
XMT: Solicit on eth0, interval 1070ms.
RCV: Advertise message on eth0 from fe80::baae:edff:fe77:7798.
[...]
XMT: Request on eth0, interval 910ms.
RCV: Reply message on eth0 from fe80::baae:edff:fe77:7798.
[...]
RCV:  | | X-- IAADDR fd11:7::175
RCV:  | | | X-- Preferred lifetime 7200.
RCV:  | | | X-- Max lifetime 7500.
RCV:  X-- Server ID: 00:01:00:01:29:d9:12:a2:02:42:0a:fe:fe:fe
message status code Success: "success"
PRC: Bound to lease 00:01:00:01:29:d9:12:a2:02:42:0a:fe:fe:fe.

The systemd-network config (as produced by netplan).

[Match]
MACAddress=xx:xx:xx:xx:xx:xx
Name=eth0

[Network]
DHCP=ipv6   <-- explicitly enabling dhcpv6
LinkLocalAddressing=ipv6
Address=192.168.0.1/24
IPv6AcceptRA=no

[Route]
Destination=0.0.0.0/0
Gateway=192.168.0.10

Any ideas as to why networkd is not launching the DHCPv6 client?

dhcpv6 systemd-networkd

1 Answers

  1. Best Answer

    Ok, it seems WithoutRA=solicit is the setting needed under [DHCPv6].

    I might file an issue with the docs, as this seems contradictory to statement in the [Network] section.

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