This article provides the supported upgrade path from VMware Cloud Foundation (VCF) 5.1.x to VCF 9.1.
VMware Cloud Foundation 5.1.x
A direct upgrade from VCF 5.1.x to VCF 9.1 is not supported.
If your environment is running VCF 5.1.x, you must first upgrade the management domain and all workload domains to VCF 5.2.x or VCF 9.0.x. Once your environment has been successfully updated to one of these intermediate versions, you can proceed with the upgrade to VCF 9.1.
For detailed instructions on upgrading your environment, refer to the following VMware Cloud Foundation documentation:
VCF 5.2.x: Upgrading VMware Cloud Foundation to 5.2.x
VCF 9.0.x: Upgrading Your VCF Management Domain to VMware Cloud Foundation 9.0
VCF 9.1.x: Upgrading to VMware Cloud Foundation 9.1