Description of problem: When creating a VM using a dual-stack network and the IPv6 Subnet is configured with ipv6_address_mode and ipv6_ra_mode as slaac and it has a dns nameserver set, the nameserver is not present on the resolv.conf of the NetworkManager. For installations that rely on the content of that file, for example OpenShift install, to generate /etc/resolv.conf, that becomes a problem. $ openstack network show f7347838-e693-4393-8ef1-9ac6a5cfeaee +---------------------------+----------------------------------------------------------------------------+ | Field | Value | +---------------------------+----------------------------------------------------------------------------+ | admin_state_up | UP | | availability_zone_hints | | | availability_zones | | | created_at | 2024-07-05T15:03:41Z | | description | | | dns_domain | | | id | f7347838-e693-4393-8ef1-9ac6a5cfeaee | | ipv4_address_scope | None | | ipv6_address_scope | None | | is_default | None | | is_vlan_transparent | False | | mtu | 1422 | | name | network-dualstack | | port_security_enabled | True | | project_id | ad715f4c418b4a3288bda53717be9c7f | | provider:network_type | None | | provider:physical_network | None | | provider:segmentation_id | None | | qos_policy_id | None | | revision_number | 7 | | router:external | Internal | | segments | None | | shared | False | | status | ACTIVE | | subnets | 3b38c62e-ca55-497f-b5a6-8bd963e0ed56, dd78e29c-1172-4c48-b608-b3808e712016 | | tags | | | updated_at | 2024-08-13T14:43:10Z | +---------------------------+----------------------------------------------------------------------------+ $ openstack subnet show subnet-dualstack-v6 +----------------------+----------------------------------------------------------------+ | Field | Value | +----------------------+----------------------------------------------------------------+ | allocation_pools | fd2e:6f44:5dd8:c956::1-fd2e:6f44:5dd8:c956:ffff:ffff:ffff:ffff | | cidr | fd2e:6f44:5dd8:c956::/64 | | created_at | 2024-07-05T15:03:47Z | | description | | | dns_nameservers | fd2e:6f44:5dd8:c956:f816:3eff:fef0:3a0 | | dns_publish_fixed_ip | None | | enable_dhcp | True | | gateway_ip | fd2e:6f44:5dd8:c956:: | | host_routes | | | id | dd78e29c-1172-4c48-b608-b3808e712016 | | ip_version | 6 | | ipv6_address_mode | slaac | | ipv6_ra_mode | slaac | | name | subnet-dualstack-v6 | | network_id | f7347838-e693-4393-8ef1-9ac6a5cfeaee | | prefix_length | None | | project_id | ad715f4c418b4a3288bda53717be9c7f | | revision_number | 1 | | segment_id | None | | service_types | None | | subnetpool_id | None | | tags | | | updated_at | 2024-08-12T15:39:26Z | +----------------------+----------------------------------------------------------------+ $ openstack server create --network network-dualstack --image CentOS-9-Stream --flavor worker --key-name key-ipv6 --security-group default test $ openstack server show 7ab723e5-47c6-463f-bddb-e9b19429a9b6 +-----------------------------+----------------------------------------------------------------------------+ | Field | Value | +-----------------------------+----------------------------------------------------------------------------+ | OS-DCF:diskConfig | MANUAL | | OS-EXT-AZ:availability_zone | nova | | OS-EXT-STS:power_state | Running | | OS-EXT-STS:task_state | None | | OS-EXT-STS:vm_state | active | | OS-SRV-USG:launched_at | 2024-08-13T14:46:00.000000 | | OS-SRV-USG:terminated_at | None | | accessIPv4 | | | accessIPv6 | | | addresses | network-dualstack=192.168.192.212, fd2e:6f44:5dd8:c956:f816:3eff:fe5b:b95c | | config_drive | | | created | 2024-08-13T14:45:56Z | | flavor | worker (31bf8ab8-57fe-4c9c-ba7f-f7eee688e0c9) | | hostId | 096f7b5a3372dee3fc7283d2a282c0b5670ea45786c6678f6c3b5082 | | id | 7ab723e5-47c6-463f-bddb-e9b19429a9b6 | | image | CentOS-9-Stream (94917fa7-ae6d-495e-9c62-889062001129) | | key_name | key-ipv6 | | name | test | | progress | 0 | | project_id | ad715f4c418b4a3288bda53717be9c7f | | properties | | | security_groups | name='default' | | status | ACTIVE | | updated | 2024-08-13T14:46:00Z | | user_id | 7999f6dc05d847539876ee0415e7415e | | volumes_attached | | +-----------------------------+----------------------------------------------------------------------------+ [cloud-user@test ~]$ cat /var/run/NetworkManager/resolv.conf # Generated by NetworkManager search openstackgate.local The same does not happen for subnets that are configured with stateful: $ openstack subnet show v6 |grep -e ipv6 -e dns -e cidr -e id | cidr | 2001:db8:2222:5555::/64 | | dns_nameservers | fd2e:6f44:5dd8:c956:f816:3eff:fef0:3a0 | | dns_publish_fixed_ip | None | | id | b3e7bf58-282e-4965-a24e-ed0758db242b | | ipv6_address_mode | dhcpv6-stateful | | ipv6_ra_mode | dhcpv6-stateful | | network_id | 0d93db16-75f4-4da4-b215-16cae9d63eb3 | | project_id | ad715f4c418b4a3288bda53717be9c7f | | segment_id | None | | subnetpool_id | None | $ openstack network show dual-stest +---------------------------+----------------------------------------------------------------------------+ | Field | Value | +---------------------------+----------------------------------------------------------------------------+ | admin_state_up | UP | | availability_zone_hints | | | availability_zones | | | created_at | 2024-08-13T15:08:50Z | | description | | | dns_domain | | | id | 0d93db16-75f4-4da4-b215-16cae9d63eb3 | | ipv4_address_scope | None | | ipv6_address_scope | None | | is_default | None | | is_vlan_transparent | False | | mtu | 1422 | | name | dual-stest | | port_security_enabled | True | | project_id | ad715f4c418b4a3288bda53717be9c7f | | provider:network_type | None | | provider:physical_network | None | | provider:segmentation_id | None | | qos_policy_id | None | | revision_number | 5 | | router:external | Internal | | segments | None | | shared | False | | status | ACTIVE | | subnets | 7ba595c8-ce3f-4e0c-8aa9-f3b10749a203, b3e7bf58-282e-4965-a24e-ed0758db242b | | tags | | | updated_at | 2024-08-13T15:21:57Z | +---------------------------+----------------------------------------------------------------------------+ $ openstack server create --network dual-stest --image CentOS-9-Stream --flavor worker --key-name key-ipv6 --security-group default test $ cat /var/run/NetworkManager/resolv.conf # Generated by NetworkManager search openstackgate.local nameserver fd2e:6f44:5dd8:c956:f816:3eff:fef0:3a0 Version-Release number of selected component (if applicable): How reproducible: Always Steps to Reproduce: 1. Create network 2. create an IPv4 subnet and add to the network for step 1 3. create an IPv6 subnet with ipv6_address_mode and ipv6_ra_mode as slaac, set a dns namserver and set the network to be of step 1 4. create a VM with that network 5. check if the content of /var/run/NetworkManager/resolv.conf contains the dns-namserver configured in the IPv6 subnet. Actual results: IPv6 dns nameserver is not available on /var/run/NetworkManager/resolv.conf Expected results: IPv6 dns nameserver is available on /var/run/NetworkManager/resolv.conf Additional info: