I tried IPv6 support in Amazon EC2 VPC. Amazon EC2 VPC uses RA and DHCPv6 for IPv6 addressing.

Problem

AFAIK, a EC2 instance receives an RA message with manged flag, then it sends a DHCPv6 solicit message to ff02::1:2. DHCPv6 server in VPC is expected to respond to solicit massages.

In case of dhclient, everything works well. But in case of systemd-networkd (or dhcpcd), it seems that DHCPv6 server ignores solicit messages (that is, no DHCPv6 advertise message appears in packets captured by tcpdump)

Environment

• Linux (coreos 1339.0.0, kernel 4.10.1)
• systemd 231
• dhcpcd 6.11.5 (by docker container with host-network and privileged mode)
• dhclient 4.3.5 (by docker container with host-network and privileged mode)

My suspicion

DHCPv6 solicit messages sent by systemd-networkd and dhcpcd have rapid-commit option. On the other hand, those sent by dhclient do not have rapid-commit option. The presence of that option is the most notable difference I've found in the solicit messages from dhclient and the others.

Question

In case of systemd-networkd (or dhcpcd), how to disable rapid-commit option ? I want to use systemd-networkd for network management.