---
title: Pause and Unpause the Bridge
lang: en-US
---


## Why do it?

The bridge is the way that assets move between blockchains.
If there is a problem with the security of the blockchain, pausing the bridge is a way to mitigate the damage until the issue is resolved.

## Who can do it?

[`OptimismPortal`](https://github.com/ethereum-optimism/optimism/blob/develop/packages/contracts-bedrock/contracts/L1/OptimismPortal.sol) has an immutable `GUARDIAN`. 
That address can call [`pause`](https://github.com/ethereum-optimism/optimism/blob/develop/packages/contracts-bedrock/contracts/L1/OptimismPortal.sol#L166-L170) and [`unpause`](https://github.com/ethereum-optimism/optimism/blob/develop/packages/contracts-bedrock/contracts/L1/OptimismPortal.sol#L175-L179).


### Changing the guardian

The guardian created by the setup script is the admin account.
This is sufficient for testing, but for a production system you would want the guardian to be a multisig with trusted security council.

The guardian is immutable, there is no way to change it while using the same contract.
Luckily, it isn't supposed to be called directly, but through a proxy.
[You can tell the proxy to go to a new contract](../build/tutorials/new-precomp.md).

## Seeing it in action

1. Set these environment variables

   | Variable | Meaning
   | - | - |
   | `PRIV_KEY` | Private key for your ADMIN account
   | `ADMIN_ADDR` | Address of the ADMIN account
   | `PORTAL_ADDR` | Portal proxy address, get from `.../optimism/packages/contracts-bedrock/deployments/getting-started/OptimismPortalProxy.json`
   | `GOERLI_RPC` | URL for an RPC to the L1 Goerli network 

1.  For using Foundry, set `ETH_RPC_URL`.

    ```sh
    export ETH_RPC_URL=$GOERLI_RPC
    ```

1. Check the balance of the ADMIN account.
   If it is too low you will not be able to submit transactions.

   ```sh
   cast balance $ADMIN_ADDR
   ```

1. Send a deposit to L2.

   ```sh
   cast send --private-key $PRIV_KEY --value 1gwei $PORTAL_ADDR
   ```

   Note the transaction hash.

1. Pause the portal.

   ```sh
   cast send --private-key $PRIV_KEY $PORTAL_ADDR "pause()"
   ```

1. Send a deposit to L2.

   ```sh
   cast send --private-key $PRIV_KEY --value 1gwei $PORTAL_ADDR
   ```

   Note the transaction hash.

1. Wait ten minutes and see which transaction(s) have been relayed using the [SDK](../build/sdk.md). 
   Use [`getMessageStatus`](https://sdk.optimism.io/classes/crosschainmessenger#getMessageStatus) to get the information.



1. Unpause the portal.

   ```sh
   cast send --private-key $PRIV_KEY $PORTAL_ADDR "pause()"
   ```