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OPNsense MCP Server

by lucamarien

OPNsense MCP Server

A secure Model Context Protocol (MCP) server for managing OPNsense firewalls through AI assistants like Claude Code, Cursor, and other MCP-compatible tools.

81 tools across 10 domains: system, firewall, network, DNS, DHCP, VPN, HAProxy, services, diagnostics, and security.

Requirements

  • Python 3.11+

  • OPNsense 24.7 or newer — the MCP server relies on the MVC-based API endpoints introduced in OPNsense 24.7. Older versions use a different API structure that is not compatible. The server auto-detects the OPNsense version on first connect and selects the correct endpoint naming (camelCase for pre-25.7, snake_case for 25.7+). OPNsense 26.x is fully supported, including its changed firmware status response format.

Related MCP server: allcanuse-mcp

Security Model

This MCP server is designed with security as the primary concern:

  • Read-only by default — write operations require explicit opt-in via OPNSENSE_ALLOW_WRITES=true

  • Savepoint/rollback — all firewall modifications use OPNsense's built-in 60-second auto-revert mechanism; changes must be explicitly confirmed or they roll back automatically

  • Endpoint blocklist — dangerous endpoints (halt, reboot, poweroff, firmware update/upgrade) are hard-blocked at the API client level and can never be called

  • API-only — no SSH access, no command execution, no direct config file manipulation

  • Local transport — STDIO only, no network-exposed HTTP/SSE endpoints

  • No credential exposure — API keys are never included in tool output, logs, or error messages

  • Input validation — hostname parameters are validated against shell metacharacter injection

  • Sensitive data stripping — config backup strips passwords and keys by default

Quick Start

1. Create an OPNsense API Key

  1. Log in to your OPNsense web interface

  2. Go to System > Access > Users

  3. Either edit an existing user or create a dedicated API user:

    • For production use, create a dedicated user (e.g., mcp-api) with only the privileges needed

    • For read-only access, assign the user to a group with read-only API access

  4. Scroll down to the API keys section and click the + button

  5. A key/secret pair will be generated and a file (apikey.txt) will be downloaded

  6. The file contains two lines — key=your-api-key-here and secret=your-api-secret-here

  7. Store these credentials securely — the secret cannot be retrieved again from OPNsense

Tip: For a read-only setup (recommended for getting started), you don't need to change any permissions — the default API access is sufficient for all read-only tools.

2. Install

# Using pip
pip install opnsense-mcp-server

# Using uv (recommended for isolated environments)
uv pip install opnsense-mcp-server

# Using Docker
docker pull lucamarien/opnsense-mcp-server

# From source
git clone https://github.com/lucamarien/opnsense-mcp-server
cd opnsense-mcp-server
pip install -e .

3. Configure Your AI Assistant

Claude Code

Add to your project's .mcp.json:

{
  "mcpServers": {
    "opnsense": {
      "command": "opnsense-mcp",
      "env": {
        "OPNSENSE_URL": "https://192.168.1.1/api",
        "OPNSENSE_API_KEY": "your-api-key-here",
        "OPNSENSE_API_SECRET": "your-api-secret-here",
        "OPNSENSE_VERIFY_SSL": "false",
        "OPNSENSE_ALLOW_WRITES": "false"
      }
    }
  }
}

Alternative: Use "command": "python", "args": ["-m", "opnsense_mcp"] if the opnsense-mcp CLI is not on your PATH.

Or add it globally to ~/.claude/claude_code_config.json.

Claude Code (Docker)

{
  "mcpServers": {
    "opnsense": {
      "command": "docker",
      "args": [
        "run", "-i", "--rm",
        "-e", "OPNSENSE_URL=https://192.168.1.1/api",
        "-e", "OPNSENSE_API_KEY=your-api-key-here",
        "-e", "OPNSENSE_API_SECRET=your-api-secret-here",
        "-e", "OPNSENSE_VERIFY_SSL=false",
        "-e", "OPNSENSE_ALLOW_WRITES=false",
        "lucamarien/opnsense-mcp-server"
      ]
    }
  }
}

Cursor

Add to your Cursor MCP settings (Settings > MCP):

{
  "mcpServers": {
    "opnsense": {
      "command": "opnsense-mcp",
      "env": {
        "OPNSENSE_URL": "https://192.168.1.1/api",
        "OPNSENSE_API_KEY": "your-api-key-here",
        "OPNSENSE_API_SECRET": "your-api-secret-here",
        "OPNSENSE_VERIFY_SSL": "false"
      }
    }
  }
}

Configuration

Environment Variable

Default

Description

OPNSENSE_URL

(required)

OPNsense API base URL (must end with /api)

OPNSENSE_API_KEY

(required)

API key from OPNsense user settings

OPNSENSE_API_SECRET

(required)

API secret from OPNsense user settings

OPNSENSE_VERIFY_SSL

true

Verify SSL certificate (false for self-signed certs)

OPNSENSE_ALLOW_WRITES

false

Enable write operations (firewall rules, service control)

Custom ports: If your OPNsense web GUI runs on a non-standard port (e.g., 10443), include it in the URL: https://192.168.1.1:10443/api

Available Tools (81)

System (7 tools)

Tool

Description

opn_system_status

System info including firmware version, product name, and architecture

opn_list_services

List all services and their running status. Params: search, limit

opn_gateway_status

Gateway availability, latency, and dpinger health checks

opn_download_config

Download config.xml backup with optional sensitive data stripping. Params: include_sensitive (default: false — passwords and keys are redacted)

opn_scan_config

Scan the full configuration, parse it into sections, and collect runtime inventory (firmware, plugins, DHCP, DNS, interfaces, services). Results are cached per session. Params: force

opn_get_config_section

Get a specific config section as structured JSON. Params: section, include_sensitive

opn_mcp_info

MCP server version, write mode status, detected OPNsense version, and API style

Network (5 tools)

Tool

Description

opn_interface_stats

Per-interface traffic statistics (bytes in/out, packets, errors)

opn_arp_table

ARP table showing IP-to-MAC address mappings

opn_ndp_table

NDP (Neighbor Discovery Protocol) table showing IPv6-to-MAC address mappings

opn_ipv6_status

IPv6 configuration and address status for all interfaces (method, live addresses, summary)

opn_list_static_routes

Configured static routes. Params: search, limit

Firewall (21 tools)

Tool

Description

Writes

opn_list_firewall_rules

List MVC firewall filter rules. Params: search, limit

No

opn_list_firewall_aliases

List alias definitions (IP lists, port groups, GeoIP, URLs). Params: search, limit

No

opn_list_nat_rules

List NAT port forwarding (DNAT) rules. Params: search, limit

No

opn_list_firewall_categories

List firewall rule categories and their UUIDs. Params: search, limit

No

opn_firewall_log

Recent firewall log entries with client-side filtering. Params: source_ip, destination_ip, action, interface, limit

No

opn_confirm_changes

Confirm pending changes, cancelling 60-second auto-rollback. Params: revision

Yes

opn_toggle_firewall_rule

Toggle a rule's enabled/disabled state with savepoint. Params: uuid

Yes

opn_add_firewall_rule

Create a new filter rule with savepoint. Params: action, direction, interface, ip_protocol, protocol, source_net, destination_net, destination_port, description

Yes

opn_delete_firewall_rule

Delete a filter rule by UUID with savepoint. Params: uuid

Yes

opn_add_alias

Create a new alias. Params: name, alias_type, content, description

Yes

opn_add_nat_rule

Create a NAT port forwarding rule with savepoint. Params: destination_port, target_ip, interface, protocol, target_port, description

Yes

opn_add_firewall_category

Create a new firewall rule category. Params: name, color

Yes

opn_delete_firewall_category

Delete a firewall rule category by UUID with savepoint. Params: uuid

Yes

opn_set_rule_categories

Assign categories to a firewall rule with savepoint. Params: uuid, categories

Yes

opn_add_icmpv6_rules

Create essential ICMPv6 rules required for IPv6 operation (NDP, RA, ping6) per RFC 4890. Params: interface

Yes

opn_update_alias

Update an existing alias (name, content, type, description). Read-modify-write. Params: uuid, name, content, description, alias_type, enabled

Yes

opn_delete_alias

Delete an alias by UUID. Check rule references first. Params: uuid

Yes

opn_toggle_alias

Toggle alias enabled/disabled state. Params: uuid

Yes

opn_update_firewall_rule

Update filter rule fields with savepoint. Params: uuid, action, direction, interface, ip_protocol, protocol, source_net, source_not, source_port, destination_net, destination_not, destination_port, gateway, log, quick, sequence, categories, description, enabled

Yes

opn_update_nat_rule

Update NAT port forwarding rule with savepoint. Params: uuid, interface, protocol, destination_port, target_ip, target_port, description, enabled

Yes

opn_delete_nat_rule

Delete a NAT port forwarding rule by UUID with savepoint. Params: uuid

Yes

DNS (13 tools)

Tool

Description

Writes

opn_list_dns_overrides

Unbound host overrides (local DNS records). Params: search, limit

No

opn_list_dns_forwards

DNS forward zones (domain-specific servers). Params: search, limit

No

opn_dns_stats

Unbound resolver statistics (queries, cache hits, uptime)

No

opn_reconfigure_unbound

Apply pending DNS resolver configuration changes

Yes

opn_add_dns_override

Add an Unbound DNS host override (A/AAAA record) and apply immediately. Params: hostname, domain, server, description

Yes

opn_list_dnsbl

List DNSBL blocklist configurations with providers and status. Params: search, limit

No

opn_get_dnsbl

Get full DNSBL configuration by UUID (providers, allowlists, settings). Params: uuid

No

opn_set_dnsbl

Update DNSBL settings (read-modify-write). Params: uuid, enabled, providers, allowlists, blocklists, wildcards, etc.

Yes

opn_add_dnsbl_allowlist

Add domains to DNSBL allowlist without overwriting. Params: uuid, domains

Yes

opn_remove_dnsbl_allowlist

Remove domains from DNSBL allowlist. Params: uuid, domains

Yes

opn_update_dnsbl

Reload DNSBL blocklist files and restart Unbound (no config change, recovery tool)

Yes

opn_update_dns_override

Update an Unbound DNS host override and apply immediately. Params: uuid, hostname, domain, server, description, enabled

Yes

opn_delete_dns_override

Delete an Unbound DNS host override and apply immediately. Params: uuid

Yes

DHCP (8 tools)

Tool

Description

Writes

opn_list_dhcp_leases

Active DHCPv4 leases from the ISC DHCP server

No

opn_list_kea_leases

DHCPv4 leases from the Kea DHCP server. Params: search, limit

No

opn_list_dnsmasq_leases

DHCPv4 and DHCPv6 leases from the dnsmasq DNS/DHCP server. Params: search, limit

No

opn_list_dnsmasq_ranges

Configured DHCP address ranges (both DHCPv4 and DHCPv6 with RA config). Params: search, limit

No

opn_add_dnsmasq_range

Create a new DHCP range (IPv4 or IPv6 with Router Advertisement configuration). Params: interface, start_addr, end_addr, prefix_len, ra_mode, lease_time, description

Yes

opn_reconfigure_dnsmasq

Apply pending dnsmasq DNS/DHCP configuration changes

Yes

opn_update_dnsmasq_range

Update a DHCP range (addresses, lease time, RA config) and apply. Params: uuid, interface, start_addr, end_addr, prefix_len, ra_mode, lease_time, description, enabled

Yes

opn_delete_dnsmasq_range

Delete a DHCP range by UUID and apply. Params: uuid

Yes

VPN (3 tools)

Tool

Description

opn_wireguard_status

WireGuard tunnel and peer status (requires os-wireguard plugin)

opn_ipsec_status

IPsec VPN tunnel status — IKE (Phase 1) and ESP/AH (Phase 2) sessions

opn_openvpn_status

OpenVPN connection status — instances, sessions, and routes

HAProxy (8 tools)

Full configuration management for the HAProxy load balancer (requires os-haproxy plugin).

Tool

Description

Writes

opn_haproxy_status

HAProxy service status and backend health

No

opn_haproxy_search

Search HAProxy resources by type. Params: resource_type (frontends/backends/servers/actions/acls/healthchecks/errorfiles/resolvers/mailers), search, limit

No

opn_haproxy_get

Get detailed configuration for a specific resource. Params: resource_type, uuid

No

opn_haproxy_configtest

Validate HAProxy configuration syntax before applying

No

opn_haproxy_add

Create a new HAProxy resource. Params: resource_type, config (dict of field values)

Yes

opn_haproxy_update

Update an existing HAProxy resource (partial updates). Params: resource_type, uuid, config

Yes

opn_haproxy_delete

Delete a HAProxy resource by UUID. Params: resource_type, uuid

Yes

opn_reconfigure_haproxy

Apply pending HAProxy configuration changes

Yes

Note: HAProxy changes do NOT use savepoint protection — they apply immediately on reconfigure. Always call opn_haproxy_configtest before opn_reconfigure_haproxy.

Services (11 tools)

Tool

Description

Writes

opn_list_acme_certs

ACME/Let's Encrypt certificates and their status. Params: search, limit

No

opn_list_cron_jobs

Scheduled cron jobs. Params: search, limit

No

opn_crowdsec_status

CrowdSec security engine status and active decisions

No

opn_crowdsec_alerts

CrowdSec security alerts (detected threats). Params: search, limit

No

opn_list_ddns_accounts

Dynamic DNS accounts and their update status. Params: search, limit

No

opn_add_ddns_account

Create a new Dynamic DNS account. Params: service, hostname, username, password, checkip, interface, description

Yes

opn_reconfigure_ddclient

Apply pending Dynamic DNS configuration changes

Yes

opn_update_ddns_account

Update a Dynamic DNS account (password is write-only). Params: uuid, service, hostname, username, password, checkip, interface, description, enabled

Yes

opn_delete_ddns_account

Delete a Dynamic DNS account by UUID. Params: uuid

Yes

opn_mdns_repeater_status

mDNS Repeater status and configuration (enabled, interfaces, blocklist). Requires os-mdns-repeater plugin

No

opn_configure_mdns_repeater

Configure mDNS Repeater for cross-VLAN device discovery (HomeKit, Chromecast, AirPlay). Params: enabled, interfaces

Yes

Diagnostics (4 tools)

Tool

Description

opn_ping

Ping a host from the firewall to test connectivity. Params: host, count (1-10, default 3)

opn_traceroute

Trace network path to a destination. Params: host, protocol (ICMP/UDP/TCP), ip_version (4/6)

opn_dns_lookup

DNS lookup from the firewall. Params: hostname, server (optional custom DNS server)

opn_pf_states

Query active PF state table. Params: search, limit (max 1000)

Security (1 tool)

Tool

Description

opn_security_audit

Comprehensive 11-area security audit: firmware, firewall rules (MVC + legacy, port grouping, insecure protocols), NAT forwarding, DNS security (DNSSEC, DoT), system hardening (SSH, HTTPS, syslog), services, certificates (ACME + system + CAs), VPN (WireGuard config, IPsec, OpenVPN), HAProxy (headers, health checks), gateways. Findings tagged with PCI DSS v4.0, BSI IT-Grundschutz, NIST 800-41, CIS compliance references.

Write Operations and Savepoints

Write operations require OPNSENSE_ALLOW_WRITES=true and use OPNsense's savepoint mechanism for safety:

  1. Before any firewall change, a savepoint is created automatically

  2. The change is applied (rule toggle, add, or delete)

  3. A 60-second countdown starts — if not confirmed, OPNsense automatically reverts the change

  4. Use opn_confirm_changes with the returned revision to make changes permanent

This means if an AI assistant makes a bad firewall change that locks you out, the change will automatically revert within 60 seconds.

Note: opn_reconfigure_unbound, opn_reconfigure_haproxy, opn_reconfigure_ddclient, opn_reconfigure_dnsmasq, and opn_configure_mdns_repeater require writes but don't use savepoints — they apply service configuration changes and are not automatically revertible.

IPv6 Support

Fully Automated via MCP

  • IPv6 Firewall Rules — Create rules with ip_protocol="inet6" (savepoint-protected)

  • HAProxy IPv6 Bindings — Frontends with [::]:443 or [2001:db8::1]:443 bind addresses

  • HAProxy IPv6 Backends — Servers with IPv6 addresses, resolvePrefer: ipv6 on backends

  • Dynamic DNS with IPv6 — DDNS accounts with IPv6-capable checkip methods

  • DHCPv6 Ranges (dnsmasq) — IPv6 DHCP ranges with Router Advertisement configuration

  • DNS AAAA Records — Unbound host overrides with IPv6 addresses

  • IPv6 Diagnostics — Traceroute with ip_version="6", ping via hostname

Requires Manual GUI Configuration

These settings lack MVC API support in OPNsense and must be configured via the web GUI:

  • WAN IPv6 setup — PPPoE with DHCPv6 prefix delegation, static IPv6, SLAAC

  • LAN IPv6 addressing — Track Interface mode, static /64 assignment, prefix ID

  • Interface assignment — Assigning physical ports to WAN/LAN/OPT roles

  • 6to4/6rd tunnels — Transition tunnel mechanisms

Known Limitations

  • ISC DHCP / Kea DHCPv6: Not implemented. Only dnsmasq (the modern default) is supported for DHCPv6 ranges and Router Advertisements. ISC DHCP is deprecated; Kea DHCPv6 lease visibility is limited in the API.

  • radvd: Not implemented as a separate tool set. Dnsmasq handles Router Advertisements natively via range configuration. Only one RA daemon should run per interface.

  • Dual-stack firewall rules: inet46 (dual-stack) works correctly in MVC API rules (opn_add_firewall_rule). However, inet46 in legacy XML filter rules (GUI) silently produces no PF output — this is a known OPNsense bug that only affects legacy rules.

  • Legacy GUI rules: Firewall rules created via the traditional OPNsense GUI are not accessible through the MVC API. Use opn_get_config_section("filter") for read-only access.

  1. Manual (GUI): Configure WAN IPv6 (DHCPv6-PD from ISP or static)

  2. Manual (GUI): Configure LAN interfaces (Track Interface mode for prefix delegation)

  3. MCP: Configure Router Advertisements via opn_add_dnsmasq_range with RA flags

  4. MCP: Create IPv6 firewall rules (ICMPv6 must be allowed for NDP/RA/PMTUD)

  5. MCP: Add IPv6 DNS records via opn_add_dns_override

  6. MCP: Configure Dynamic DNS with IPv6 checkip method

  7. MCP: Add IPv6 bind addresses to HAProxy frontends

  8. MCP: Verify with opn_ping, opn_traceroute (ip_version="6"), opn_gateway_status

Version Compatibility

OPNsense Version

Status

24.7 (Thriving Tiger)

Supported

25.1 (Ultimate Unicorn)

Supported

25.7 (Visionary Viper)

Supported (auto-detects snake_case API)

26.1+

Supported

The server automatically detects the OPNsense version on first connection and selects the correct API endpoint naming convention (camelCase for pre-25.7, snake_case for 25.7+).

Note on firewall rules: opn_list_firewall_rules shows rules managed via the MVC/automation API. Rules configured through the OPNsense GUI use a legacy format not accessible via this API. This is a known OPNsense limitation.

Troubleshooting

Connection Issues

"Connection refused" or timeout errors

  • Verify OPNSENSE_URL ends with /api (e.g., https://192.168.1.1/api)

  • If using a non-standard port, include it: https://192.168.1.1:10443/api

  • Ensure the OPNsense web GUI is accessible from the machine running the MCP server

SSL certificate errors

  • For self-signed certificates (default OPNsense setup), set OPNSENSE_VERIFY_SSL=false

  • For production, install a proper certificate on OPNsense and keep OPNSENSE_VERIFY_SSL=true

Authentication Issues

401 Unauthorized

  • Verify OPNSENSE_API_KEY and OPNSENSE_API_SECRET are correct

  • API keys are case-sensitive — copy them exactly from the downloaded apikey.txt

  • Check that the API user is not disabled in OPNsense

  • Verify the API user has sufficient privileges for the operations you're attempting

403 Forbidden

  • The API user may lack permissions for the requested endpoint

  • For write operations, ensure OPNSENSE_ALLOW_WRITES=true is set

Tool-Specific Issues

opn_list_firewall_rules returns empty results

  • This tool only shows MVC/automation rules, not legacy GUI rules

  • Create rules via the automation API or opn_add_firewall_rule to see them

opn_ping times out

  • The firewall may not have a route to the target host

  • Check gateway status with opn_gateway_status

  • Default timeout is 30 seconds (30 poll cycles)

opn_download_config shows [REDACTED] values

  • This is the default behavior for security. Pass include_sensitive=true to include passwords and keys (use with caution in AI conversations)

Write operations fail with "writes not enabled"

  • Set OPNSENSE_ALLOW_WRITES=true in your MCP server configuration

  • This is intentionally disabled by default for safety

Savepoint confirmation fails

  • The revision parameter must match exactly what was returned by the write operation

  • Confirmations must happen within 60 seconds or the change auto-reverts

Diagnostic Commands

If you need to debug the MCP server:

# Test API connectivity directly
curl -k -u "your-key:your-secret" https://your-opnsense-ip/api/core/firmware/status

# Run the server directly
python -m opnsense_mcp

# Run tests to verify installation
pytest -v

Development

# Clone and install dev dependencies
git clone https://github.com/lucamarien/opnsense-mcp-server
cd opnsense-mcp-server
pip install -e ".[dev]"

# Run all tests (no real OPNsense needed — all tests use mocked API)
pytest -v

# Full CI pipeline (lint, format, type check, security scan, tests)
make validate

# Individual checks
ruff check src/ tests/          # Lint (includes bandit security checks)
ruff format src/ tests/          # Format
mypy src/ --strict               # Type checking

Best Practices

Domain-specific guides for common firewall configuration tasks:

These guides show real-world MCP tool usage patterns and explain the security considerations behind each approach.

Contributing

See CONTRIBUTING.md for detailed guidelines. Key points:

  1. All tests must use mocked API responses — never connect to a real OPNsense

  2. No overlapping tools — each tool must have a distinct purpose

  3. Write clear docstrings — they're the AI's only guide to tool selection

  4. Return structured data (dicts), not formatted strings

  5. Run make validate before submitting

License

MIT

Install Server
A
license - permissive license
A
quality
C
maintenance

Maintenance

Maintainers
Response time
2dRelease cycle
4Releases (12mo)
Commit activity

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