how much is the number of practical nodes supported by XBee -PRO Digimesh2.4 network

The size of the network is a function of the size of your network and the amount of data throughput and the network topology. Keeping in mind that size and results can very, a Digi Mesh network has been test to Aprox 500 nodes. If you want to limit the amount of rout discoveries or broadcast transmissions, you can support up to 128 nodes using unicast addressing.