What network access do I need when I restoring files using RMAN?
If you are using the 11g duplicate from active database option, the only port that needs to be open is the listener port (usually 1521). If you are using any other options to copy your files to the standby host, the required ports for the protocol that you use (scp/ftp/nfs ...)

Apart from the 11g 'from active database' option, RMAN does only read backupfiles that are present on the node on which the restore/clone is to be taking place. Present in this setting means that they thould be readable. The can be on [n]fs or tape, as long as your host can read them it is ok.

I hope this helps