OPNsense MCP Server

A Model Context Protocol (MCP) server for comprehensive OPNsense firewall management. This server enables AI assistants like Claude to directly manage firewall configurations, diagnose network issues, and automate complex networking tasks.

Features

🔥 Firewall Management

• Complete CRUD operations for firewall rules
• Proper handling of API-created "automation rules"
• Inter-VLAN routing configuration
• Batch rule creation and management
• Enhanced persistence with multiple fallback methods

🌐 NAT Configuration (SSH-based)

• Outbound NAT rule management
• NAT mode control (automatic/hybrid/manual/disabled)
• No-NAT exception rules for inter-VLAN traffic
• Automated DMZ NAT issue resolution
• Direct XML configuration manipulation

🔍 Network Diagnostics

• Comprehensive routing analysis
• ARP table inspection with vendor identification
• Interface configuration management
• Network connectivity troubleshooting
• Auto-fix capabilities for common issues

🖥️ SSH/CLI Execution

• Direct command execution on OPNsense
• Configuration file manipulation
• System-level operations not available via API
• Service management and restarts

📊 Additional Capabilities

• VLAN management
• DHCP lease viewing and management
• DNS blocklist configuration
• HAProxy load balancer support
• Configuration backup and restore
• Infrastructure as Code support

Installation

Prerequisites

• Node.js 18+ or Bun 1.0+
• OPNsense firewall (v24.7+ recommended)
• API credentials for OPNsense
• SSH access (optional, for advanced features)

Quick Start with npm

1. Install the package:

npm install -g opnsense-mcp-server

2. Create a .env file with your credentials:

# Required
OPNSENSE_HOST=https://your-opnsense-host:port
OPNSENSE_API_KEY=your-api-key
OPNSENSE_API_SECRET=your-api-secret
OPNSENSE_VERIFY_SSL=false

# Optional - for SSH features
OPNSENSE_SSH_HOST=your-opnsense-host
OPNSENSE_SSH_USERNAME=root
OPNSENSE_SSH_PASSWORD=your-password
# Or use SSH key
# OPNSENSE_SSH_KEY_PATH=~/.ssh/id_rsa

# Recommended for a new/production router — see "Safety Modes" below
# OPNSENSE_READ_ONLY=true

3. Start the MCP server:

opnsense-mcp-server

⚠️ Safety Modes (read this before pointing at a production router)

By default this server can make live, immediate changes to your firewall — add/delete rules, change NAT, restart services, run whitelisted shell commands over SSH. Two environment variables (operator-only — a tool call can never set or override them) add a safety net:

Variable	Effect
OPNSENSE_READ_ONLY=true	Every mutating API call and every non-read-only SSH command is rejected before it's sent. Write-capable tools are also hidden from the tool list, so the model never sees them as an option.
OPNSENSE_DRY_RUN=true	Mutating calls are simulated instead of sent — you get a log line and a synthetic success response describing what would have happened, with no request reaching the router.

Both are enforced at the two lowest-level chokepoints this server uses to reach the router — the API client and the SSH executor — so they apply uniformly across all 140+ tools, not on a per-tool basis. If both are set, OPNSENSE_READ_ONLY wins.

# First time pointing this at a real router? Start here:
OPNSENSE_READ_ONLY=true

# Once you trust it, watch what it would do before going live:
OPNSENSE_DRY_RUN=true

# Remove both once you're confident.

See CONFIGURATION.md for the config reference, or docs/features/safety-modes.md for how it works under the hood.

Quick Start with Bun (Faster)

Bun provides significantly faster startup times and better performance.

1. Install Bun (if not already installed):

curl -fsSL https://bun.sh/install | bash

2. Clone and install:

git clone https://github.com/vespo92/OPNSenseMCP.git
cd OPNSenseMCP
bun install

3. Create your .env file (same as npm version above)

4. Run with Bun:

# Development with hot reload
bun run dev:bun

# Production
bun run start:bun

Using Bun with Claude Desktop

{
  "mcpServers": {
    "opnsense": {
      "command": "bun",
      "args": ["run", "/path/to/OPNSenseMCP/src/index.ts"],
      "env": {
        "OPNSENSE_HOST": "https://your-opnsense:port",
        "OPNSENSE_API_KEY": "your-key",
        "OPNSENSE_API_SECRET": "your-secret",
        "OPNSENSE_VERIFY_SSL": "false"
      }
    }
  }
}

Usage with Claude Desktop (npm)

Add to your Claude Desktop configuration (claude_desktop_config.json):

{
  "mcpServers": {
    "opnsense": {
      "command": "npx",
      "args": ["opnsense-mcp-server"],
      "env": {
        "OPNSENSE_HOST": "https://your-opnsense:port",
        "OPNSENSE_API_KEY": "your-key",
        "OPNSENSE_API_SECRET": "your-secret",
        "OPNSENSE_VERIFY_SSL": "false"
      }
    }
  }
}

Common Use Cases

Fix DMZ NAT Issues

// Automatically fix DMZ to LAN routing
await mcp.call('nat_fix_dmz', {
  dmzNetwork: '10.0.6.0/24',
  lanNetwork: '10.0.0.0/24'
});

Create Firewall Rules

// Allow NFS from DMZ to NAS
await mcp.call('firewall_create_rule', {
  action: 'pass',
  interface: 'opt8',
  source: '10.0.6.0/24',
  destination: '10.0.0.14/32',
  protocol: 'tcp',
  destination_port: '2049',
  description: 'Allow NFS from DMZ'
});

Diagnose Routing Issues

// Run comprehensive routing diagnostics
await mcp.call('routing_diagnostics', {
  sourceNetwork: '10.0.6.0/24',
  destNetwork: '10.0.0.0/24'
});

Execute CLI Commands

// Run any OPNsense CLI command
await mcp.call('system_execute_command', {
  command: 'pfctl -s state | grep 10.0.6'
});

MCP Tools Reference

The server provides 50+ MCP tools organized by category:

Firewall Tools

• firewall_list_rules - List all firewall rules
• firewall_create_rule - Create a new rule
• firewall_update_rule - Update existing rule
• firewall_delete_rule - Delete a rule
• firewall_apply_changes - Apply pending changes

NAT Tools

• nat_list_outbound - List outbound NAT rules
• nat_set_mode - Set NAT mode
• nat_create_outbound_rule - Create NAT rule
• nat_fix_dmz - Fix DMZ NAT issues
• nat_analyze_config - Analyze NAT configuration

Network Tools

• arp_list - List ARP table entries
• routing_diagnostics - Diagnose routing issues
• routing_fix_all - Auto-fix routing problems
• interface_list - List network interfaces
• vlan_create - Create VLAN

System Tools

• system_execute_command - Execute CLI command
• backup_create - Create configuration backup
• service_restart - Restart a service

For a complete list, see docs/api/mcp-tools.md.

Documentation

• Quick Start Guide
• Configuration Guide
• NAT Management
• SSH/CLI Execution
• Firewall Rules
• Safety Modes (Dry-Run & Read-Only)
• Troubleshooting

Testing

The repository includes comprehensive testing utilities:

# Test NAT functionality
npx tsx scripts/test/test-nat-ssh.ts

# Test firewall rules
npx tsx scripts/test/test-rules.ts

# Test routing diagnostics
npx tsx scripts/test/test-routing.ts

# Run all tests
npm test

Development

Building from Source

git clone https://github.com/vespo92/OPNSenseMCP.git
cd OPNSenseMCP
npm install
npm run build

Project Structure

OPNSenseMCP/
├── src/                 # Source code
│   ├── api/            # API client
│   ├── resources/      # Resource implementations
│   └── index.ts        # MCP server entry
├── docs/               # Documentation
├── scripts/            # Utility scripts
│   ├── test/          # Test scripts
│   ├── debug/         # Debug utilities
│   └── fixes/         # Fix scripts
└── dist/               # Build output

Troubleshooting

API Authentication Failed

• Verify API key and secret are correct
• Ensure API access is enabled in OPNsense
• Check firewall rules allow API access

SSH Connection Failed

• Verify SSH credentials in .env
• Ensure SSH is enabled on OPNsense
• Check user has appropriate privileges

NAT Features Not Working

• NAT management requires SSH access
• Add SSH credentials to environment variables
• Test with: npx tsx scripts/test/test-nat-ssh.ts

Contributing

Contributions are welcome! Please see CONTRIBUTING.md for guidelines.

License

This project is licensed under the MIT License - see the LICENSE file for details.

Support

• Issues: GitHub Issues
• Discussions: GitHub Discussions
• Documentation: Full Documentation

Acknowledgments

• Built for use with Anthropic's Claude
• Implements the Model Context Protocol
• Designed for OPNsense firewall

---

Version: 0.8.2 | Status: Production Ready | Last Updated: August 2025