> ## Documentation Index
> Fetch the complete documentation index at: https://optimism-373f39ad-mds-systemconfig-remove-unused-getters.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Legacy Geth configuration options

> Reference for Legacy Geth (l2geth) environment variables and the RPC methods routed to it.

This page catalogues the environment variables Legacy Geth (`l2geth`) accepts and the RPC methods your execution client routes to it.
For what Legacy Geth is and how to set it up, see the [Legacy Geth guide](/node-operators/guides/configuration/legacy-geth).

Legacy Geth applies only to networks that upgraded through Bedrock, such as OP Mainnet, where it serves execution requests and chain data for pre-Bedrock blocks.

## Environment variables

Legacy Geth accepts the following environment variables:

| Variable                   | Description                    | Default                               |
| -------------------------- | ------------------------------ | ------------------------------------- |
| `USING_OVM`                | **Required**. Enables OVM mode | N/A (must be set to `true`)           |
| `ETH1_SYNC_SERVICE_ENABLE` | Enables L1 sync service        | `true` (set to `false` for read-only) |
| `RPC_API`                  | Enabled RPC APIs               | `eth,net,web3`                        |
| `RPC_ADDR`                 | RPC listening address          | `localhost`                           |
| `RPC_CORS_DOMAIN`          | CORS domains                   | `localhost`                           |
| `RPC_ENABLE`               | Enable RPC server              | `false`                               |
| `RPC_PORT`                 | RPC port                       | `8545`                                |
| `RPC_VHOSTS`               | Virtual hosts                  | `localhost`                           |

<Warning>
  `USING_OVM=true` must always be set.
  Without it, `l2geth` panics at startup or returns invalid execution traces.
</Warning>

## Execution-client routing flag

Both op-reth and op-geth use the same `--rollup.historicalrpc` flag to route pre-Bedrock requests to Legacy Geth.
The flag takes the URL of the Legacy Geth RPC endpoint, for example `--rollup.historicalrpc=http://localhost:8545`.

## RPC methods routed to Legacy Geth

This section describes op-reth.
When `--rollup.historicalrpc` is set, op-reth forwards requests that target pre-Bedrock blocks to Legacy Geth and serves everything else directly.
This covers both methods that require transaction execution (which op-reth cannot perform for pre-Bedrock blocks) and methods that read pre-Bedrock block or transaction data.
Methods not listed below (for example `eth_getLogs`) are never routed to Legacy Geth.

<Info>
  op-geth behaved differently: it served pre-Bedrock block and transaction data locally from its migrated database and routed only execution methods to Legacy Geth.
  op-geth has reached end-of-support and this behavior is no longer documented here; see the [op-geth deprecation notice](/notices/archive/op-geth-deprecation).
</Info>

### State and execution methods

Routed to Legacy Geth when the method's block parameter refers to a pre-Bedrock block:

* `eth_call`
* `eth_estimateGas`
* `eth_createAccessList`
* `eth_getBalance`
* `eth_getCode`
* `eth_getStorageAt`
* `eth_getTransactionCount`
* `eth_getProof`
* `debug_traceCall`

### Block data methods

Routed to Legacy Geth when the requested block is pre-Bedrock, or when the requested block hash is unknown to op-reth:

* `eth_getBlockByNumber` / `eth_getBlockByHash`
* `eth_getBlockReceipts`
* `eth_getHeaderByNumber` / `eth_getHeaderByHash`
* `eth_getBlockTransactionCountByNumber` / `eth_getBlockTransactionCountByHash`
* `eth_getUncleCountByBlockNumber` / `eth_getUncleCountByBlockHash`
* `eth_getUncleByBlockNumberAndIndex` / `eth_getUncleByBlockHashAndIndex`
* `eth_getTransactionByBlockNumberAndIndex` / `eth_getTransactionByBlockHashAndIndex`
* `eth_getRawTransactionByBlockNumberAndIndex` / `eth_getRawTransactionByBlockHashAndIndex`
* `debug_traceBlockByNumber` / `debug_traceBlockByHash`

### Transaction data methods

Routed to Legacy Geth when the transaction belongs to a pre-Bedrock block, or when the transaction is unknown to op-reth:

* `eth_getTransactionByHash`
* `eth_getTransactionReceipt`
* `eth_getRawTransactionByHash`
* `debug_traceTransaction`

### `eth_getBlockReceipts` emulation

Legacy Geth (`l2geth`) predates `eth_getBlockReceipts` and does not implement it.
op-reth forwards the request first; if Legacy Geth responds that the method does not exist, op-reth fetches the block's transaction hashes from Legacy Geth and assembles the response from one `eth_getTransactionReceipt` call per transaction.
Receipts are returned in transaction order and passed through verbatim, with their legacy fields intact — exactly what a forwarded `eth_getTransactionReceipt` returns for the same transactions.
A block unknown to Legacy Geth returns `null`, and a block without transactions returns `[]`.