# Multinetwork Node¶

Tezos is run on several networks, such as Mainnet (the main network) and various Test Networks. Some users may also want to run their own networks for various reasons. Networks differ in various 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 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. See also Alias Versus Explicit Configuration for a discussion regarding what happens when you update your node.

## Built-In Networks¶

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 Delphinet:

tezos-node config init --data-dir ~/tezos-delphinet --network delphinet
tezos-node identity generate --data-dir ~/tezos-delphinet
tezos-node run --data-dir ~/tezos-delphinet


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

• mainnet (this is the default)

• sandbox

• delphinet (available from version 7.4)

• edonet (available from version 8.0~rc2)

If you did not initialize your node configuration, or if your configuration file contains no 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 Delphinet:

tezos-node run --data-dir ~/tezos-delphinet --network delphinet


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

## Custom Networks¶

If the network you want to connect to is not in the list of built-in networks, you can configure a custom network in the configuration file. Here is an example configuration file for Mainnet:

{
"p2p": {},
"network": {
"genesis": {
"timestamp": "2018-06-30T16:07:32Z",
"block": "BLockGenesisGenesisGenesisGenesisGenesisf79b5d1CoW2",
"protocol": "Ps9mPmXaRzmzk35gbAYNCAw6UXdE2qoABTHbN2oEEc1qM7CwT9P"
},
"chain_name": "TEZOS_MAINNET",
"old_chain_name": "TEZOS_BETANET_2018-06-30T16:07:32Z",
"incompatible_chain_name": "INCOMPATIBLE",
"sandboxed_chain_name": "SANDBOXED_TEZOS_MAINNET",
{
"level": 28082,
"replacement_protocol": "PsYLVpVvgbLhAhoqAkMFUo6gudkJ9weNXhUYCiLDzcUpFpkk8Wt"
},
{
"level": 204761,
"replacement_protocol": "PsddFKi32cMJ2qPjf43Qv5GDWLDPZb3T3bF6fLKiF5HtvHNU7aP"
}
],
"user_activated_protocol_overrides": [
{
"replaced_protocol": "PsBABY5HQTSkA4297zNHfsZNKtxULfL18y95qb3m53QJiXGmrbU",
"replacement_protocol": "PsBabyM1eUXZseaJdmXFApDSBqj8YBfwELoxZHHW77EMcAbbwAS"
}
],
"default_bootstrap_peers": [ "boot.tzbeta.net" ]
}
}


This is equivalent to using config init --network mainnet, or "network": "Mainnet" in the configuration file (or to doing nothing, as Mainnet is the default), except that you will not automatically get updates to the list of bootstrap peers and user-activated upgrades (see Alias Versus Explicit Configuration).

• genesis is the description of the genesis block, i.e. the first block of the chain. Inspect the genesis block using tezos-client rpc get /chains/main/blocks/0 to find these values.

• chain_name is the name of the network (nodes only talk to other nodes which use the same network name).

• old_chain_name is usually the same as chain_name, except for networks that were renamed.

• incompatible_chain_name is a name which must be different from chain_name and old_chain_name. It is thus ensured to be incompatible. It is used for testing purposes.

• sandboxed_chain_name is the name of the network in sandbox mode. It can be the same as chain_name but it is safer to pick a different name.

• user_activated_upgrades is the list of past user-activated upgrades. Each item has a field level, which is the level at which the protocol must be changed, and a field replacement_protocol, which is the hash of the protocol to switch to.

• user_activated_protocol_overrides is the list of past user-activated protocol overrides. Each item has a field replaced_protocol and a field replacement_protocol. Both are protocol hashes. If replaced_protocol is to be activated using on-chain voting, replacement_protocol is activated instead.

• default_bootstrap_peers is the list of addresses of default bootstrap peers. They are only used if p2p.bootstrap_peers is not present in the configuration file, and --no-bootstrap-peers is not given on the command-line.

## Genesis Parameters¶

In addition to the above fields, you can also specify custom genesis parameters. For instance, if your genesis protocol is proto_genesis, you can specify the activation key:

{
"p2p": {},
"network": {
"genesis": { ... },
"genesis_parameters": {
"context_key": "sandbox_parameter",
"values": {
"genesis_pubkey": "edpk..."
}
},
...
}
}


The genesis_parameters object contains:

• context_key, the name of the key in the context part of the storage, whose value must be modified (if omitted, the default context key is sandbox_parameter);

• values, which contains the protocol parameters.

In the above example, we set the genesis_pubkey parameter of proto_genesis.

Note that the genesis parameters that you specify in the configuration file can be overridden by the --sandbox parameter on the command-line. Similarly, if you are using a built-in network and if this built-in network comes with genesis parameters, you can override them with --sandbox.

## Alias Versus Explicit Configuration¶

If you use one of the Built-In Networks, the configuration file stores the name of the network to connect to. For instance, if you configured it to connect to Delphinet, it will contain something like:

{
"p2p": {},
"network": "delphinet"
}


For Mainnet, it would contain mainnet, or nothing as this is actually the default.

When you update your node to new versions, built-in network parameters may change. For instance, the list of bootstrap peers may be updated with new addresses. Or, new user-activated upgrades or user-activated protocol overrides may be added. Because the configuration file only contains the name of the network and not its parameters, it will automatically use the updated values.

However, if you configure Custom Networks, the configuration file will no longer contain an alias such as mainnet or delphinet. Instead, it will explicitly contain the list of bootstrap peers, user-activated upgrades and user-activated protocol overrides that you specify. This means that when you update your node, updates to built-in network parameters will have no effect.

As a consequence, if you configure a custom network, you need to update its parameters yourself. Reciprocally, if you wish to update your node to a new version but do not wish to use the new built-in network parameters, you can configure a custom network.

## Development¶

The list of built-in networks is in src/bin_node/node_config_file.ml. Edit the builtin_blockchain_networks_with_tags variable in this file to add or remove built-in networks.

To be able to connect to multiple networks without having to download the protocols, and to provide all the relevant baker / endorser / accuser binaries, all current and past protocols are compiled and linked. This means that if you patch the client commands for a protocol, you should patch the other protocols as well (at least the ones which are still in use).