You can indeed! But there are some constraints. A Corda Network is really an instance of the following:
A network map - an IP-address book for nodes to lookup other nodes
A permissioning service - issues certificates to allow entities onto the network
A Notary - signs transactions to prevent double-spends
these tools have only been internally deployed in infrastructure provisioned by the Corda Foundation. The networks that are available now are UAT (user acceptance testing) and the Corda Network