GETH configuration - what is the difference between '--testnet' and '--network 3'?

Question

I'm reading GETH Command-Line Options Guide, which says:

--testnet            Ropsten network: pre-configured proof-of-work test network
--networkid value    Network identifier (integer, 1=Frontier, 2=Morden (disused), 3=Ropsten, ...)

What exactly is the difference between --testnet and --network 3?

Do I have to use both, or can I use either one?

Thank you!

Answer 1

Each network has an ID and a name.

The network ID of Ropsten is 3.

The network ID of the Main Network is 1.

--network 3 evaluates to Ropsten, which also happens to be the default test network in the GETH client.