> For the complete documentation index, see [llms.txt](https://bitnet-whitepaper.gitbook.io/developer-docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://bitnet-whitepaper.gitbook.io/developer-docs/bitnet-ops-handbook/run-an-ibc-relayer.md).

# Run an IBC Relayer

### Running an IBC Relayer for BitNet

Inter-Blockchain Communication (IBC) enables BitNet to securely send tokens and data to other chains in the Cosmos ecosystem. Relayers are off-chain agents that **listen for packets** on one chain and **transmit them to the other**.

This guide walks you through setting up an IBC relayer between **BitNet** and another IBC-enabled chain using **Hermes**.

***

#### What is an IBC Relayer?

An IBC relayer:

* Connects two blockchain networks.
* Listens for IBC packets on one chain.
* Relays those packets to the destination chain.
* Requires full nodes for both chains and funds for gas fees.

***

#### Minimum Requirements

* 4+ physical CPU cores (8 threads)
* 32 GB RAM
* 1TB+ NVMe SSD
* High open file limits (adjust `ulimit -n`)

***

#### Prerequisites

* A running **BitNet full node** (see earlier guides).
* A full node for the **counterparty chain** (e.g., Cosmos Hub).
* Port configuration for both nodes to avoid conflicts.
* Funds in both chains for relayer fees.

***

#### Step 1: Configure Nodes

**BitNet Node (`~/.bitnetd/config/`):**

* `app.toml`:

```toml
[grpc]
enable = true
address = "0.0.0.0:9090"
```

* `config.toml`:

```toml
pprof_laddr = "localhost:6060"
[rpc]
laddr = "tcp://127.0.0.1:26657"
[p2p]
laddr = "tcp://0.0.0.0:26656"
```

**Counterparty Node (e.g., Cosmos Hub):**

* Offset ports to avoid collision:

```toml
grpc = "0.0.0.0:9092"
pprof_laddr = "localhost:6062"
rpc = "tcp://127.0.0.1:26757"
p2p = "tcp://0.0.0.0:26756"
```

***

#### Step 2: Install Hermes

Install Rust & dependencies:

```bash
curl https://sh.rustup.rs -sSf | sh
source $HOME/.cargo/env
sudo apt install build-essential git pkg-config libssl-dev librust-openssl-dev
```

Clone and build Hermes:

```bash
git clone https://github.com/informalsystems/ibc-rs.git hermes
cd hermes
git checkout v0.12.0
cargo install ibc-relayer-cli --bin hermes --locked
```

Create Hermes config folders:

```bash
mkdir -p ~/.hermes/config ~/.hermes/keys
cp config.toml ~/.hermes/
```

***

#### Step 3: Configure Hermes

Edit `~/.hermes/config.toml` and set up both chains:

```toml
[[chains]]
id = 'cosmoshub-4'
rpc_addr = 'http://127.0.0.1:26757'
grpc_addr = 'http://127.0.0.1:9092'
websocket_addr = 'ws://127.0.0.1:26757/websocket'
[chains.packet_filter]
policy = 'allow'
list = [['transfer', 'channel-292']]

[[chains]]
id = 'bitnet-mainnet'
rpc_addr = 'http://127.0.0.1:26657'
grpc_addr = 'http://127.0.0.1:9090'
websocket_addr = 'ws://127.0.0.1:26657/websocket'
address_type = { derivation = 'ethermint', proto_type = { pk_type = '/ethermint.crypto.v1.ethsecp256k1.PubKey' } }
[chains.packet_filter]
policy = 'allow'
list = [['transfer', 'channel-3']]
```

***

#### Step 4: Add Relayer Keys

Use your mnemonic for both chains:

```bash
hermes keys restore cosmoshub-4 -m "your 24-word mnemonic"
hermes keys restore bitnet-mainnet -m "your 24-word mnemonic"
```

Ensure both accounts have enough tokens to cover transaction fees.

***

#### Step 5: Validate & Start

```bash
hermes config validate
hermes health-check
hermes start
```

You’ll see logs showing relayed packets.

***

#### Step 6: Maintenance & Monitoring

**Query unreceived packets:**

```bash
hermes query packet unreceived-packets cosmoshub-4 transfer channel-292
hermes query packet unreceived-packets bitnet-mainnet transfer channel-3
```

**Clear stuck packets:**

```bash
hermes clear packets cosmoshub-4 transfer channel-292
hermes clear packets bitnet-mainnet transfer channel-3
```