Most VMware appliances (vCenter Appliance, VMware Support Appliance, vRealize Orchestrator) have the so called VAMI: the VMware Appliance Management Interface, generally served via https on port 5480. VAMI offers a variety of functions, including "check updates" and "install updates". Some appliances offer to check/install updates from a connected CD iso, but the default is always to check online. How does that work?
VMware uses a dedicated website to serve the updates: vapp-updates.vmware.com. Each appliance is configured with a repository URL: https://vapp-updates.vmware.com/vai-catalog/valm/vmw/PRODUCT-ID/VERSION-ID . The PRODUCT-ID is a hexadecimal code specific for the product. vRealize Orchestrator uses 00642c69-abe2-4b0c-a9e3-77a6e54bffd9, VMware Support Appliance uses 92f44311-2508-49c0-b41d-e5383282b153, vCenter Server Appliance uses 647ee3fc-e6c6-4b06-9dc2-f295d12d135c. The VERSION-ID contains the current appliance version and appends ".latest": 126.96.36.19900.latest, 188.8.131.52.latest, 184.108.40.206.latest.
The appliance will check for updates by retrieving the repository URL /manifest/manifest-latest.xml . This xml contains the latest available version in
With this information, you can setup your own local repository (for cases where internet access is impossible from the virtual appliances), or you can even execute the procedure manually. Be aware that manual update would be unsupported. Using a different repository is supported by a subset of VMware appliances (e.g. VCSA, VRO) but not all (VMware Support Appliance).