Hi,
Basically VUM and VC is one to one mapping. However, you can add multiple vCenter to vum from Update manager utility but that is not supported by VMware.
VUM has a utility called VMwareUpdateManagerUtility.exe in which we can re-register the vCenter Server . For ex we can install the VUM plugin to the first VCSA 1.1.1.1 and update the ESX host. Later we can re-configure the VUM by running the utility and it will ask for the option to give the VC name or IP in which we can provide the second VC IP address.
Hope that answer your query.
Regards,
Sachin Bhardwaj
