apache/cassandra · critical · ConfigurationException

Set rpc_address OR rpc_interface, not both

Error message

Set rpc_address OR rpc_interface, not both

What it means

DatabaseDescriptor.applyAddressConfig requires the client (native protocol RPC) server to bind via rpc_address OR rpc_interface. Having both set in cassandra.yaml is ambiguous, so startup fails with this ConfigurationException, mirroring the listen_address/listen_interface rule.

Source

Thrown at src/java/org/apache/cassandra/config/DatabaseDescriptor.java:1547

        if (config.broadcast_address != null)
        {
            try
            {
                broadcastAddress = InetAddress.getByName(config.broadcast_address);
            }
            catch (UnknownHostException e)
            {
                throw new ConfigurationException("Unknown broadcast_address '" + config.broadcast_address + '\'', false);
            }

            if (broadcastAddress.isAnyLocalAddress())
                throw new ConfigurationException("broadcast_address cannot be a wildcard address (" + config.broadcast_address + ")!", false);
        }

        /* Local IP, hostname or interface to bind RPC server to */
        if (config.rpc_address != null && config.rpc_interface != null)
        {
            throw new ConfigurationException("Set rpc_address OR rpc_interface, not both", false);
        }
        else if (config.rpc_address != null)
        {
            try
            {
                rpcAddress = InetAddress.getByName(config.rpc_address);
            }
            catch (UnknownHostException e)
            {
                throw new ConfigurationException("Unknown host in rpc_address " + config.rpc_address, false);
            }
        }
        else if (config.rpc_interface != null)
        {
            rpcAddress = getNetworkInterfaceAddress(config.rpc_interface, "rpc_interface", config.rpc_interface_prefer_ipv6);
        }
        else
        {

View on GitHub (pinned to 88fd0f6a0e)

Solutions

1. Keep only one of rpc_address or rpc_interface in cassandra.yaml; comment the other out.
2. Most deployments should set rpc_address to the node IP (or 0.0.0.0 to bind all interfaces) and leave rpc_interface commented.
3. Restart the node after fixing the config.

Example fix

# before (cassandra.yaml)
rpc_address: 0.0.0.0
rpc_interface: eth0
# after
rpc_address: 0.0.0.0
# rpc_interface: eth0

raise 'Set rpc_address OR rpc_interface, not both' if yaml['rpc_address'] && yaml['rpc_interface']

catch (ConfigurationException e) { logger.error("cassandra.yaml rpc address conflict: {}", e.getMessage()); System.exit(2); }

When it happens

Trigger: cassandra.yaml contains non-null values for both rpc_address and rpc_interface.

Common situations: Uncommenting rpc_interface: eth0 while the default rpc_address: localhost is still active; automation tools that add rpc_interface without removing rpc_address.

Understand the failure class

Background: Conflicting config options: "cannot be used together" — configuration validation errors across open-source libraries — this error's family across 162 libraries.

Related errors

• Unknown host in rpc_address
• Set listen_address OR listen_interface, not both
• Unknown listen_address '
• listen_address cannot be a wildcard address (
• Unknown broadcast_address '

AI-assisted analysis of apache/cassandra@88fd0f6a0e (2026-09-10). Data as JSON: /api/errors/8b0e6969eb7d8bc0. Report an issue: GitHub.