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Relay Node Configuration

A relay node accepts connections from the network and forwards blocks and transactions to your block producer. It has a public IP address; your block producer does not.

Before continuing, complete Installing cardano-node and download your network's configuration files as described in Running cardano-node.

Test on preprod first

Run through the full setup on the Pre-Production testnet before touching mainnet. Swap mainnet for preprod in every path and URL below.

Relay topology​

Your relay connects outward to:

  • Your block producer — as a private localRoots entry, never advertised
  • Bootstrap peers — trusted relays from founding organizations, used for initial sync (Praos mode)
  • The wider network — via ledger peer discovery once synced

Example relay topology for mainnet:

{
  "localRoots": [
    {
      "accessPoints": [
        { "address": "YOUR-BLOCK-PRODUCER-IP", "port": 6000 }
      ],
      "advertise": false,
      "hotValency": 1,
      "warmValency": 2,
      "trustable": false
    }
  ],
  "bootstrapPeers": [
    { "address": "backbone.cardano.iog.io",               "port": 3001 },
    { "address": "backbone.mainnet.emurgornd.com",         "port": 3001 },
    { "address": "backbone.mainnet.cardanofoundation.org", "port": 3001 }
  ],
  "publicRoots": [
    {
      "accessPoints": [
        { "address": "relays-new.cardano-mainnet.iohk.io", "port": 3001 }
      ],
      "advertise": false
    }
  ],
  "useLedgerAfterSlot": 128908821
}

Key points:

  • advertise: false on the block producer entry — its address must never be shared with the network.
  • useLedgerAfterSlot should match the value in the official topology.json for your network. Do not set it to -1 on a relay.
  • For preprod, use the bootstrap peers and useLedgerAfterSlot value from the downloaded preprod topology.

See Topology for full field documentation, Genesis mode configuration, and peer connection targets.

Mithril relay (optional, required for Mithril signing)​

note

This section only applies if you are running a Mithril signer on your block producer to participate in Mithril snapshot certification. It is not required to operate a stake pool.

The Mithril relay is a Squid forward proxy that runs on the Cardano relay machine. It routes traffic between the Mithril signer on your block producer and the external Mithril aggregator, keeping the block producer isolated from the public internet.

Key configuration points:

  • Listening port — 3132 is recommended
  • Source restriction — only the block producer's internal IP is allowed to connect
  • Destination restriction — only HTTPS traffic to *.mithril.network is permitted
  • Header anonymization — request headers are stripped to avoid disclosing information about the block producer
  • Caching — disabled; the proxy only forwards traffic

After setting up the proxy, point the Mithril signer on the block producer at it by setting RELAY_ENDPOINT=http://<relay-internal-ip>:3132 in the signer's environment.

For the complete setup including build commands, Squid configuration, and the systemd service unit, see Set up the Mithril relay node in the Mithril documentation.

Further reading: