Build an n8n Telegram Bot for OPNsense NAT & Firewall Rules

Build an n8n Telegram bot that lets approved users propose OPNsense NAT and firewall rules—then confirms, audits, and applies them safely

This n8n automation turns plain-language requests sent via Telegram into structured OPNsense firewall and destination NAT rules. It uses OpenAI to classify, normalize, and security-audit each request against existing rules, then asks for confirmation with inline buttons before calling the OPNsense API to apply the change.

What this workflow does

• Telegram access control: Triggers on a Telegram message (or inline-button callback) and checks the sender against an allowlist stored in an n8n Data Table.
• Request classification: For new messages, it normalizes the text and uses OpenAI to classify the request as either a firewall rule or destination NAT (port forward). Unknown requests receive an “unknown” notice.
• Structured rule extraction & validation: It uses OpenAI to extract a structured rule, normalizes it for OPNsense formatting, and validates required fields and network value formats.
• Security audit with context: It pulls existing firewall rules, existing destination NAT rules, and interface details from OPNsense, then uses OpenAI to audit for issues and overlaps.
• Human confirmation: Sends a formatted summary and audit result to Telegram with Confirm/Cancel inline buttons, and stores the pending request in an n8n Data Table.
• Apply via OPNsense API: On confirmation, it calls the appropriate OPNsense API endpoint, applies the configuration, updates status, and notifies success/failure in Telegram.

Use cases

• Let approved admins request OPNsense changes from a chat workflow (fast, consistent, and auditable).
• Standardize port forwards and firewall rule creation with validation and overlap detection.
• Operational teams prototype NAT/firewall updates while maintaining a confirmation gate.

Technical details

• Integrations: Telegram Trigger (bot + credentials), OPNsense API (API credentials).
• Core logic nodes: if, set, code, form, no op, switch.
• AI-assisted processing: OpenAI classification, structured extraction, normalization, and security auditing against existing OPNsense rules.
• State management: n8n Data Table for allowlist and pending requests.

Ideal for n8n users, automation engineers, and SaaS operators who need a professional Telegram-to-OPNsense NAT & firewall rules workflow with safety checks and approval.