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Connect to a testnet

Run Besu as an execution client with any consensus client on the Holesky, Sepolia, and Ephemery testnets.

If you're using Teku as a consensus client, you can follow the Besu and Teku testnet tutorial.

note

Sepolia is a permissioned network and you can't run a validator client on it without requesting to become a validator first. You can connect your consensus client using the beacon node only, without any validator duties.

note

Ephemery is a single network that resets to the genesis block after a set period. The network focuses on short-term, intensive testing use cases. This approach avoids issues like insufficient testnet funds, inactive validators, and state bloat that long-running testnets face.

Prerequisites​

Steps​

1. Generate the shared secret​

Run the following command:

openssl rand -hex 32 | tr -d "\n" > jwtsecret.hex

You will specify jwtsecret.hex when starting Besu and the consensus client. This is a shared JWT secret the clients use to authenticate each other when using the Engine API.

2. Generate validator keys​

If you're running the consensus client as a beacon node only, skip to the next step.

If you're also running the consensus client as a validator client, create a test Ethereum address (you can do this in MetaMask). Fund this address with testnet ETH (32 ETH and gas fees for each validator) using a faucet. See the list of Holesky faucets, Sepolia faucets, and Ephemery faucets.

note

If you can't get testnet ETH using the faucet, you can ask for help on the EthStaker Discord.

Generate validator keys for one or more validators using the Holesky Staking Launchpad, Ephemery Staking Launchpad, or request to become validator on Sepolia.

info

Save the password you use to generate each key pair in a .txt file. You should also have a .json file for each validator key pair.

3. Start Besu​

Run the following command or specify the options in a configuration file:

besu \
  --network=holesky           \
  --rpc-http-enabled=true     \
  --rpc-http-host=0.0.0.0     \
  --rpc-http-cors-origins="*" \
  --rpc-ws-enabled=true       \
  --rpc-ws-host=0.0.0.0       \
  --host-allowlist="*"        \
  --engine-host-allowlist="*" \
  --engine-rpc-enabled        \
  --engine-jwt-secret=<path to jwtsecret.hex>

Specify the path to the jwtsecret.hex file generated in step 1 using the --engine-jwt-secret option.

You can modify the option values and add other command line options as needed.

4. Start the consensus client​

Refer to your consensus client documentation to configure and start the consensus client.

info

If you're running a validator client, make sure you set a fee recipient address.

If you're using Teku, follow the Besu and Teku testnet tutorial.

5. Wait for the clients to sync​

After starting Besu and the consensus client, your node starts syncing and connecting to peers.

{"@timestamp":"2023-02-03T04:43:49,555","level":"INFO","thread":"main","class":"DefaultSynchronizer","message":"Starting synchronizer.","throwable":""}
{"@timestamp":"2023-02-03T04:43:49,556","level":"INFO","thread":"main","class":"FastSyncDownloader","message":"Starting sync","throwable":""}
{"@timestamp":"2023-02-03T04:43:49,559","level":"INFO","thread":"main","class":"Runner","message":"Ethereum main loop is up.","throwable":""}
{"@timestamp":"2023-02-03T04:43:53,106","level":"INFO","thread":"Timer-0","class":"DNSResolver","message":"Resolved 2409 nodes","throwable":""}
{"@timestamp":"2023-02-03T04:45:04,803","level":"INFO","thread":"nioEventLoopGroup-3-10","class":"SnapWorldStateDownloader","message":"Downloading world state from peers for pivot block 16545859 (0x616ae3c4cf85f95a9bce2814a7282d75dc2eac36
cb9f0fcc6f16386df70da3c5). State root 0xa7114541f42c62a72c8b6bb9901c2ccf4b424cd7f76570a67b82a183b02f25dc pending requests 0","throwable":""}
{"@timestamp":"2023-02-03T04:46:04,834","level":"INFO","thread":"EthScheduler-Services-3 (batchPersistAccountData)","class":"SnapsyncMetricsManager","message":"Worldstate download progress: 0.08%, Peer count: 8","throwable":""}
{"@timestamp":"2023-02-03T04:48:01,840","level":"INFO","thread":"EthScheduler-Services-3 (batchPersistAccountData)","class":"SnapsyncMetricsManager","message":"Worldstate download progress: 0.23%, Peer count: 8","throwable":""}
{"@timestamp":"2023-02-03T04:49:09,931","level":"INFO","thread":"EthScheduler-Services-3 (batchPersistAccountData)","class":"SnapsyncMetricsManager","message":"Worldstate download progress: 0.41%, Peer count: 11","throwable":""}
{"@timestamp":"2023-02-03T04:50:12,466","level":"INFO","thread":"EthScheduler-Services-3 (batchPersistAccountData)","class":"SnapsyncMetricsManager","message":"Worldstate download progress: 0.61%, Peer count: 10","throwable":""}
{"@timestamp":"2023-02-03T04:51:20,977","level":"INFO","thread":"EthScheduler-Services-3 (batchPersistAccountData)","class":"SnapsyncMetricsManager","message":"Worldstate download progress: 0.75%, Peer count: 10","throwable":""}
{"@timestamp":"2023-02-03T04:51:28,985","level":"INFO","thread":"EthScheduler-Services-29 (importBlock)","class":"FastImportBlocksStep","message":"Block import progress: 180400 of 16545859 (1%)","throwable":""}

If you're running the consensus client as a beacon node only, you're all set. If you're also running the consensus client as a validator client, ensure your clients are fully synced before submitting your staking deposit in the next step. This can take several days.

6. Stake ETH​

Stake your testnet ETH for one or more validators using the Holesky Staking Launchpad or Ephemery Staking Launchpad.

You can check your validator status by searching your Ethereum address on the Holesky Beacon Chain explorer or Ephemery Beacon Chain explorer. It may take up to multiple days for your validator to be activated and start proposing blocks.