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IDProjectCategoryView StatusLast Update
0015833CentOS-7cloud-initpublic2019-02-15 23:59
Reporterdekimsey 
PrioritynormalSeverityminorReproducibilityalways
Status newResolutionopen 
Product Version7.6.1810 
Target VersionFixed in Version 
Summary0015833: ipv6 router advertisements are disabled due to IPV6_AUTOCONF=no
DescriptionI tested this with an Amazon VPC with working IPv6 configuration (the amazon-ami's work fine) using cloud-init 18.2_1.

If one assigns an IPv6 address to the machine via DHCP6. Cloudinit sets up a configuration that apparently disables router advertisements due to side-effect. As a result the box has no default gateway and is unable to send IPv6 traffic (Network unreachable errors).

I found someone else mentioning this issue here and their work-around: https://access.redhat.com/solutions/347693#comment-520173

And it basically came down to having IPV6_AUTOCONF=no which sets the sysctl setting, net.ipv6.conf.eth0.accept_ra=0. Disabling router advertisements.

Overriding IPV6_AUTOCONF in /etc/sysconfig/network-scripts to yes enables the seemingly correct functionality. This appears to be set by cloud-init in /usr/lib/python2.7/site-packages/cloudinit/net/sysconfig.py.
Steps To Reproduce1. Verify ipv6 ip: `ip a show dev eth0`
2. Verify no default route: `ip -6 r show dev eth0`
3. Verify ping fails: `ping6 -c1 ipv6.google.com`
4. Set IPV6_AUTOCONF=yes in /etc/sysconfig/network-scripts
5. Restart networking: `sudo systemctl restart network`
6. Verify default route: `ip -6 r show dev eth0 | grep default`
7. Verify ping succeeds: `ping6 -c1 ipv6.google.com`
Tagscloud-init, IPv6, network
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Issue History

Date Modified Username Field Change
2019-02-15 23:59 dekimsey New Issue
2019-02-15 23:59 dekimsey Tag Attached: cloud-init
2019-02-15 23:59 dekimsey Tag Attached: IPv6
2019-02-15 23:59 dekimsey Tag Attached: network