Document dual-stack ShiftStack installer host config reqs

Resolves OCPBUGS-25223

modules/install-osp-deploy-dualstack.adoc

@@ -138,4 +138,30 @@ platform:
 <4> Specify the dual-stack network details that are used by all the nodes across the cluster.
 <5> The CIDR of any subnet specified in this field must match the CIDRs listed on `networks.machineNetwork`.
 <6> You can specify a value for either `name` or `id`, or both.
-<7> Specifying the `network` under the `ControlPlanePort` field is optional.
+<7> Specifying the `network` under the `ControlPlanePort` field is optional.
+
+[NOTE]
+====
+When using an installation host in an isolated dual-stack network, the IPv6 address may not be reassigned correctly upon reboot. 
+
+To resolve this problem on {op-system-base-full} 8, create a file called `/etc/NetworkManager/system-connections/required-rhel8-ipv6.conf` that contains the following configuration:
+
+[source,text]
+----
+[connection]
+type=ethernet
+[ipv6]
+addr-gen-mode=eui64
+method=auto
+----
+
+To resolve this problem on {op-system-base} 9, create a file called `/etc/NetworkManager/conf.d/required-rhel9-ipv6.conf` that contains the following configuration:
+
+[source,text]
+----
+[connection]
+ipv6.addr-gen-mode=0
+----
+
+After you create and edit the file, reboot the installation host.
+====

modules/install-osp-dualstack.adoc

@@ -3,7 +3,7 @@
 // * installing/installing_openstack/installing-openstack-installer-custom.adoc
 :_mod-docs-content-type: CONCEPT
 [id="install-osp-dualstack_{context}"]
-= Optional: Configuring a cluster with dual-stack networking
+= Configuring a cluster with dual-stack networking
 
 :FeatureName: Dual-stack configuration for OpenStack