Once the hosts have been added to the VxRail cluster, you can add them to the cluster in VMware Cloud Foundation.
If the cluster to which you are adding hosts uses a static IP pool for the Host Overlay Network TEPs, that pool must include enough IP addresses for the hosts you are adding. The number of IP addresses required depends on the number of pNICs on the ESXi hosts that are used for the vSphere Distributed Switch that handles host overlay networking. For example, a host with four pNICs that uses two pNICs for host overlay traffic requires two IP addresses in the static IP pool.