You can perform an installation or upgrade using the parcel format and when using parcels, only the Cloudera Manager Server requires access to the Cloudera public repositories. Distribution of the parcels to worker hosts is done between the Cloudera Manager Server and the worker hosts. See Parcels for more information. If you want to install using the traditional packages, hosts only require access to the installation files.
For both parcels and packages, it is also possible to create local repositories that serve these files to the hosts that are being upgraded. If you have established local repositories, no access to the Cloudera public repository is required. For more information, see Creating and Using a Package Repository for Cloudera Manager.