In this chapter, we will see how Tezos is multi-network. We will learn what the "main network" and the "test networks" are and finally, we will discover how to configure our node on a chosen network.

## Mainnet​

The Tezos network is the current incarnation of the Tezos blockchain. The Tezos network has been live and open since June 30th 2018, when the genesis block was created, and the tez were allocated to the donors of the July 2017 ICO.

## Multinetwork Node​

Tezos is run on several networks, such as the Mainnet (the main network) and various testnets (test networks). Some users may also want to run their own networks for various reasons. Networks differ in multiple ways:

• they start from their own genesis block
• they have different names so that nodes know not to talk to other networks
• they may run (or have run) different protocols
• protocols may run with different constants (for instance, test networks move faster)
• they have different bootstrap peers (nodes that the new nodes connect to initially)
• they may have had user-activated upgrades or user-activated protocol overrides to change the protocol without going through the voting process.

By default, the multinetwork node connects to Mainnet. To connect to other networks, you can either use one of the Built-In Networks or configure the node to connect to Custom Networks.

## Built-In Networks​

### Test Networks​

Mainnet is the main Tezos network, and as such, it is not appropriate for testing. Other networks are available for this. Test networks usually run with different constants to speed up the chain.

To fund any addresses, go to teztnets.xyz and select the faucet according to your testnet.

The last two built-in networks to be used as a test network are:

### Network configuration​

The simplest way to select the network to connect to is to use the --network option when you initialize your node configuration. For instance, to run on Kathmandunet:

./tezos-node config init --data-dir /tezos-kathmandunet --network kathmandunet./tezos-node identity generate --data-dir /tezos-kathmandunet./tezos-node run --data-dir /tezos-kathmandunet

Once initialized, the node remembers its network settings on subsequent runs and reconnects to the same network every time you run it. If you specify a different network when running the node again, it will refuse to start. In order to switch to a different network, you need to either reinitialize it with a different data directory using the --data-dir option or remove everything from the existing data directory, which defaults to ~/.tezos-node (and also initialize again).

The --network option is not case-sensitive and can be used with the following built-in networks:

• mainnet (this is the default)
• kathmandunet
• ghostnet
• jakartanet
• sandbox

If you did not initialize your node configuration or if your configuration file doesn't contain a "network" field, the node assumes you want to run Mainnet. You can use the --network option with tezos-node run to make sure your node runs on the expected network. For instance, to make sure that it runs on Kathmandunet:

./tezos-node run --data-dir ~/tezos-kathmandunet --network kathmandunet

This command will fail with an error if the configured network is not Kathmandunet. The node also displays the chain name (such as TEZOS_MAINNET) when it starts.