# Besu Configuration: Mainnet vs Chain 138 Comparison

**Last Updated:** 2026-01-31  
**Document Version:** 1.0  
**Status:** Active Documentation

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## Command Comparison

### Ethereum Mainnet Configuration

```bash
besu \
--network=mainnet \
--sync-mode=FULL \
--rpc-http-enabled \
--rpc-http-api=ETH,NET,WEB3 \
--rpc-http-cors-origins="*" \
--rpc-http-host=0.0.0.0 \
--rpc-http-port=8545
```

**This configuration:**
- ✅ Connects to **Ethereum Mainnet** (chain ID 1)
- ✅ Downloads entire mainnet blockchain
- ✅ No genesis file needed (uses mainnet genesis)
- ✅ Public network with public discovery
- ✅ No permissioning
- ✅ Read-only APIs (ETH, NET, WEB3)

---

### Chain 138 Equivalent Configuration

For your **private/permissioned chain 138** network, the equivalent would be:

```bash
besu \
--data-path=/data/besu \
--genesis-file=/genesis/genesis.json \
--network-id=138 \
--sync-mode=FULL \
--rpc-http-enabled \
--rpc-http-api=ETH,NET,WEB3 \
--rpc-http-cors-origins="*" \
--rpc-http-host=0.0.0.0 \
--rpc-http-port=8545 \
--permissions-nodes-config-file-enabled=true \
--permissions-nodes-config-file=/permissions/permissions-nodes.toml \
--static-nodes-file=/genesis/static-nodes.json \
--discovery-enabled=false \
--p2p-host=0.0.0.0 \
--p2p-port=30303 \
--miner-enabled=false
```

**Key Differences:**

| Setting | Mainnet | Chain 138 |
|---------|---------|-----------|
| Network | `--network=mainnet` | `--network-id=138` |
| Genesis | Auto (mainnet) | `--genesis-file=/genesis/genesis.json` |
| Permissioning | Disabled | **Enabled** (local nodes only) |
| Discovery | Enabled (public) | Disabled (private) |
| Static Nodes | None | Required (`static-nodes.json`) |
| Node Allowlist | None | Required (`permissions-nodes.toml`) |
| Consensus | PoS (mainnet) | QBFT (your network) |

---

## Important Notes

### ❌ Don't Use Mainnet Config for Chain 138

The mainnet configuration you showed **will NOT work** for your chain 138 network because:

1. **`--network=mainnet`** will connect to Ethereum mainnet (chain ID 1), not your chain 138
2. **No genesis file** - mainnet uses hardcoded genesis, your network needs a custom genesis
3. **No permissioning** - mainnet is public, your network is permissioned
4. **Public discovery** - mainnet discovers any node, your network only connects to allowlisted nodes

### ✅ Use Chain 138 Configuration

Your current chain 138 configuration (in TOML format) already has all the correct settings:
- `network-id=138` (not mainnet)
- `genesis-file=/genesis/genesis.json` (required)
- `permissions-nodes-config-file-enabled=true` (required for private network)
- `discovery-enabled=false` (for VMID 2500 - strict local/permissioned nodes only)

---

## Current Chain 138 Configuration (VMID 2500)

Your current configuration is correct for chain 138:

```toml
# config-rpc-core.toml (VMID 2500)
data-path="/data/besu"
genesis-file="/genesis/genesis.json"
network-id=138
sync-mode="FULL"
rpc-http-enabled=true
rpc-http-api=["ETH","NET","WEB3","ADMIN","DEBUG","TXPOOL"]
permissions-nodes-config-file-enabled=true
permissions-nodes-config-file="/permissions/permissions-nodes.toml"
static-nodes-file="/genesis/static-nodes.json"
discovery-enabled=false
```

---

## If You Need Mainnet Access

If you want to run a separate Besu node for **Ethereum mainnet** (separate from chain 138), you would:

1. Use a **separate data directory** (different from `/data/besu`)
2. Run on **different ports** (e.g., 8547, 8548)
3. Use the mainnet configuration you showed
4. This would be a **completely separate node** from your chain 138 network

**Example separate mainnet node:**

```bash
besu \
--data-path=/data/besu-mainnet \
--network=mainnet \
--sync-mode=FULL \
--rpc-http-enabled \
--rpc-http-api=ETH,NET,WEB3 \
--rpc-http-cors-origins="*" \
--rpc-http-host=0.0.0.0 \
--rpc-http-port=8547 \
--rpc-ws-port=8548
```

This would run alongside your chain 138 nodes but be completely separate.

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