The following information is based off of this guide created by Osmosis Team.

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Minimum Requirements

  • 8-core (4 physical core), x86_64 architecture processor
  • 32 GB RAM (or equivalent swap file set up)
  • 1TB+ nVME drives
  • If running many nodes on a single VM, ensure your open files limit is increased

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Prerequisites

In this guide, we will be relaying between Neutron and Cosmos Hub. When setting up your Cosmos Hub and Neutron full nodes, be sure to offset the ports being used in both the app.toml and config.toml files of the respective chains (we will show how to do this below).

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Neutron Node Settings

Here we will leave grpc server on port 9090 in the app.toml directory: 
nano $HOME/.neutrond/config/app.toml

[grpc]

# Enable defines if the gRPC server should be enabled.
enable = true

# Address defines the gRPC server address to bind to.
address = "0.0.0.0:9090"
Here we will leave the pprof_laddr set to port 6060, rpc laddr to port 26657, and p2p laddr to 26656 in the config.toml directory: 
nano $HOME/.neutrond/config/config.toml

# pprof listen address (https://golang.org/pkg/net/http/pprof)
pprof_laddr = "localhost:6060"

[rpc]

# TCP or UNIX socket address for the RPC server to listen on
laddr = "tcp://127.0.0.1:26657"

[p2p]

# Address to listen for incoming connections
laddr = "tcp://0.0.0.0:26656"

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Target Chain Node Settings

Here we will set grpc server to port 9092 in the app.toml directory: 
nano $HOME/.gaiad/config/app.toml

[grpc]

# Enable defines if the gRPC server should be enabled.
enable = true

# Address defines the gRPC server address to bind to.
address = "0.0.0.0:9092"
Here I will set the pprof_laddr to port 6062, rpc laddr to port 26757, and p2p laddr to 26756 in the config.toml directory: 
nano $HOME/.gaiad/config/config.toml

# pprof listen address (https://golang.org/pkg/net/http/pprof)
pprof_laddr = "localhost:6062"

[rpc]

# TCP or UNIX socket address for the RPC server to listen on
laddr = "tcp://127.0.0.1:26757"

[p2p]

# Address to listen for incoming connections
laddr = "tcp://0.0.0.0:26756"

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Install Rust Dependencies

Install the following rust dependencies: 
curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh

source $HOME/.cargo/env
sudo apt-get install pkg-config libssl-dev

sudo apt install librust-openssl-dev build-essential git

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Build & setup Hermes

Use rust version 1.76.0 to install, otherwise it might not compile!
This will install hermes into $HOME/.cargo/bin/ directory: 
cargo install ibc-relayer-cli --bin hermes --locked --version 1.6.0
Make hermes config & keys directory, copy config-template to config directory: 
mkdir -p $HOME/.hermes
mkdir -p $HOME/.hermes/keys
cp config.toml $HOME/.hermes
Check hermes version & config dir setup: 
hermes version
Expected output: 
2023-08-07T15:27:49.236821Z  INFO ThreadId(01) running Hermes v1.10.1
hermes 1.10.1

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Edit Hermes Config

Edit hermes config (use ports according to the port configuration we set above, add only chains you want to relay): 
nano $HOME/.hermes/config.toml
Neutron introduces smart-contract level callbacks for IBC packets. From an IBC relayer’s perspective, this means that custom application logic can be executed when a packet is submitted to Neutron, which can potentially drain the relayer’s funds. This naturally brings us to a situation in which protocols would prefer to set up their own relayers and restrict the channels they are willing to relay for.
For example, you can do this by adding a chains.packet_filter config: 
[[chains]]
id = 'cosmoshub-4'
rpc_addr = 'http://127.0.0.1:26757'
grpc_addr = 'http://127.0.0.1:9092'
event_source = { mode = 'push', url = 'ws://127.0.0.1:26757/websocket', batch_delay = '200ms' }
rpc_timeout = '10s'
account_prefix = 'cosmos'
key_name = 'cosmos'
address_type = { derivation = 'cosmos' }
store_prefix = 'ibc'
default_gas = 2000000
max_gas = 10000000
gas_price = { price = 0.005, denom = 'uatom' }
gas_adjustment = 0.1
max_msg_num = 25
max_tx_size = 180000
clock_drift = '10s'
max_block_time = '10s'
trusting_period = '14days'
memo_prefix = ''
trust_threshold = { numerator = '1', denominator = '3' }
[chains.packet_filter]
policy = 'allow'
list = [
    # allow relaying only for chanels created by a certain contract
    ['icacontroller-neutron14hj2tavq8fpesdwxxcu44rty3hh90vhujrvcmstl4zr3txmfvw9s5c2epq*', '*'],
]

[[chains]]
id = 'neutron-1'
# Whether or not this is a CCV consumer chain. Default: false
# Only specify true for CCV consumer chain (Neutron), but NOT for sovereign chains.
ccv_consumer_chain = true
rpc_addr = 'http://127.0.0.1:26657'
grpc_addr = 'http://127.0.0.1:9090'
event_source = { mode = 'push', url = 'ws://127.0.0.1:26657/websocket', batch_delay = '200ms' }
rpc_timeout = '10s'
account_prefix = 'neutron'
key_name = 'neutron'
address_type = { derivation = 'cosmos' }
store_prefix = 'ibc'
default_gas = 5000000
max_gas = 15000000
gas_price = { price = 0.0026, denom = 'untrn' }
gas_adjustment = 0.1
max_msg_num = 20
max_tx_size = 209715
clock_drift = '20s'
max_block_time = '10s'
trusting_period = '10days'
memo_prefix = 'Relayed by Czar'
trust_threshold = { numerator = '1', denominator = '3' }
[chains.packet_filter]
policy = 'allow'
list = [
    # allow relaying only for chanels created by a certain contract
    ['icacontroller-neutron14hj2tavq8fpesdwxxcu44rty3hh90vhujrvcmstl4zr3txmfvw9s5c2epq*', '*'],
]
Please refer to the official Hermes documentation if you want more deep understanding of config.

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Add Relayer Wallet

Add your relayer wallet to Hermes’ keyring (located in $HOME/.hermes/keys):
Best practice is to use the same mnemonic over all networks. Do not use your relaying-addresses for anything else because it will lead to account sequence errors.
hermes keys restore cosmoshub-4 -m "24-word mnemonic seed"
hermes keys restore neutron-1 -m "24-word mnemonic seed"
Ensure this wallet has funds in both NTRN and ATOM in order to pay the fees required to relay.

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Final Checks

You can validate your hermes configuration file: 
hermes config validate
Expected output: 
INFO ThreadId(01) using default configuration from '/home/relay/.hermes/config.toml'
Success: "validation passed successfully"
Perform health check to see if all connected nodes are up and synced: 
hermes health-check
Expected output: 
INFO ThreadId(01) using default configuration from '/home/relay/.hermes/config.toml'
INFO ThreadId(01) telemetry service running, exposing metrics at http://0.0.0.0:3001/metrics
INFO ThreadId(01) starting REST API server listening at http://127.0.0.1:3000
INFO ThreadId(01) [cosmoshub-4] chain is healthy
INFO ThreadId(01) [neutron-1] chain is healthy

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Start Relaying

When your nodes are fully synced you can start the hermes daemon: 
hermes start
Watch hermes’ output for successfully relayed packets or any errors. It will try & clear any unreceived packets after startup has completed.
It is strongly recommended to run the Relayer as a daemon service to ensure automatic restarts and continuous operation.