Looking at the changelog of 1.38.0:
* Fix bug setting priority for IP addresses. https://gitlab.freedesktop.org/NetworkManager/NetworkManager/-/blob/nm-1-38/NEWS So it looks like Ubuntu just introduced that bug by upgrading to 1.36.6. Please either backport it from 1.38.0 or revert to 1.36.4. ** Description changed: My network has both DHCPv6 and SLAAC for IPv6. From both a privacy perspective and readability reasons, DHCPv6 should *always* be preferred over SLAAC addresses when available. NetworkManager has always been able to adhere to that by simply setting ip6.privacy=0 for the connection. So if you would - for instance - run `curl ifconfig.co`, the DHCPv6 address would be used to connect to the outside world. Since the update to 1.36.6, this is no longer the case. NetworkManager now routes outgoing traffic through the SLAAC address, even if ip6.privacy=0 is set for the connection. Setting net.ipv6.conf.all.use_tempaddr = 0 and net.ipv6.conf.<interface>.use_tempaddr = 0 with sysctl also no longer has any effect. - Physically removing the SLAAC addresses or disabling RA's altogether is - the only way to stop NetworkManager from prefering SLAAC over DHCPv6 - now. + Removing the SLAAC addresses with `ip addr del` or disabling RA's + altogether is the only way to stop NetworkManager from prefering SLAAC + over DHCPv6 now. Looking at the changelog of NetworkManager 1.36.6, things regarding IP address order and temporary addresses have been changed in that release: https://gitlab.freedesktop.org/NetworkManager/NetworkManager/-/blob/nm-1-36/NEWS When running `ip -6 a`, the list now sorts SLAAC addresses above DHCPv6 addresses. With NetworkManager 1.36.4 this was not the case. Unfortunately, this introduced this bug, which is really breaking a lot of my use cases. I should note that the bug is not present in NetworkManager 1.38.0 on Debian sid. That just prefers DHCPv6 addresses when available, like it should. -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1977619 Title: DHCPv6 addresses are no longer preferred over SLAAC addresses To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/network-manager/+bug/1977619/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs