From Release 3.9 onwards, VMware Cloud Foundation on VxRail allows you to expand a cluster with the hosts residing in multiple L2 network domains (different VLANs and subnets).
For the management domain or the first cluster in the workload domain, the management VLAN should be stretched across all the L2 domains where the hosts of the cluster reside.
For information on expanding a cluster that needs cluster spanning, follow the steps in the VxRail documentation. For information on adding hosts, see Add the VxRail Hosts to the Cluster in VMware Cloud Foundation.