On Fri, Dec 02, 2016 at 12:25:44PM +0100, Bernhard Schmidt wrote: > thanks for providing an AWS EC2 Image with Debian Jessie. > > AWS is now supporting IPv6 on EC2 instances, see > > https://aws.amazon.com/de/blogs/aws/new-ipv6-support-for-ec2-instances-in-virtual-private-clouds/. > > The support is currently limited to the zone us-east2, but should be > available in all regions shortly. The provisioning of the IPv6 address > on the machine is done through stateful DHCPv6. > > For this /etc/network/interfaces needs to be amended with > > iface eth0 inet6 dhcp Unfortunately this breaks networking for instances in subnets with IPv6 *disabled*, which is likely the vast majority of them for the forseeable future. What seems to happen is that eth0 is brought up, and dhclient runs twice, once for each supported protocol. eth0 is properly configured with an IPv4 address, but (after a timeout) the IPv6 dhclient reports a failure, and ifup returns nonzero. I haven't looked deeply into exactly what happens next, but the end result is that cloud-init never runs, so the instance doesn't get properly configured. Most notably this means that ssh keys aren't installed. I've investigated a number of possible solutions to this, but haven't come up with anything better than shell script kludges. For example, it could work to run the IPv6 dhclient from a post-up script associated with eth0. Note that my testing has been with the stretch AMIs generated from https://anonscm.debian.org/cgit/cloud/fai-cloud-images.git/ so it's possible the jessie images will behave slightly differently, but I expect them to have similar problems. noah
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