What is a Captive Portal, and where do you encounter it in everyday life?

A web-based authentication gate that intercepts HTTP/HTTPS traffic and redirects users to a login page before granting network access.

* Captive Portal redirect-and-authenticate flow on the firewall. *

Everyday examples:

• Hotel Wi-Fi: connect → open browser → forced to a landing page asking for room number / accept ToS.
• Airport / café Wi-Fi: same pattern.
• Corporate guest networks: visitor logs in with email or sponsored credentials.

How the FW does it:

1. User opens any website.
2. FW sees no auth session → instead of forwarding, returns an HTTP redirect to the captive portal page.
3. User logs in (web form, certificate, Kerberos, etc.).
4. FW caches the user→IP binding for the session timeout.
5. Subsequent traffic from that IP is allowed under the user's identity.

Tip: Captive Portal = the firewall pretends to be the website you wanted, just long enough to ask "who are you?"

Go deeper:

• Captive portal (Wikipedia) — the HTTP-redirect mechanism, OS detection probes, and why HTTPS requests can't be silently redirected.