802.1X and EAP Walkthrough: EAP-TLS, PEAP and EAP-TTLS
Follow an enterprise Wi-Fi login message by message between the client, the AP and the RADIUS server, then break it on purpose and see where each failure stops the exchange.
How to use this tool controls and what to look for
Pick an EAP method and follow the login message by message between the client, the AP and the RADIUS server. Then break it on purpose.
Controls to change
- EAP method: compare EAP-TLS (TLS 1.2 and 1.3), PEAP (MSCHAPv2) and EAP-TTLS (PAP).
- What goes wrong: choose a failure: an expired server certificate, a rejected client certificate, a wrong password, a different EAP method or a wrong RADIUS shared secret.
- RADIUS round-trip time (AP ↔ server): make the server further away.
- Server certificate chain size: make the certificate chain larger.
- EAP fragment size (bytes): change how the certificates are split into pieces.
What to look for
- EAP travels in EAPOL frames between the client and the AP, and in RADIUS packets between the AP and the server.
- Each failure stops the exchange at a different point. A wrong shared secret gets no answer at all, only retransmissions.
- A large certificate chain and a slow RADIUS server multiply the round trips, and the login gets slower.
- At the end, the MSK from the login becomes the PMK for the 4-way handshake.
About this tool
Follow a WPA2/WPA3-Enterprise login message by message between the client (supplicant), the AP (authenticator) and the RADIUS server: the identity exchange, the TLS handshake with its certificate fragments, the login inside the tunnel and the keys that come out at the end. Choose EAP-TLS with TLS 1.2 or 1.3, PEAP with MSCHAPv2 or EAP-TTLS with PAP, set the RADIUS round-trip time and the certificate size, and break the login on purpose: an untrusted or expired certificate, a wrong password, a method mismatch, a wrong RADIUS shared secret or a server that doesn't answer. The ladder shows where each failure stops and what each side logs.
What you'll learn
- How EAP travels in EAPOL frames between the client and the AP, and in RADIUS packets between the AP and the server
- How EAP-TLS, PEAP and EAP-TTLS differ: what proves the server, what proves the client, and what is hidden in the tunnel
- Why large certificate chains and a distant RADIUS server make logins slow
- How the MSK from the login becomes the PMK for the 4-way handshake
Common questions
What is the difference between PEAP and EAP-TLS?
EAP-TLS proves both sides with certificates, so the client needs its own certificate and no password is used. PEAP proves only the server with a certificate, builds a TLS tunnel, and then checks a username and password (usually MSCHAPv2) inside it.
Why does my client fail with an untrusted certificate?
The client checks the server's certificate chain against the CAs it trusts and the server name it was configured with. If the CA isn't trusted or the name doesn't match, it stops the TLS handshake and the login fails, which protects the password from a fake access point.
What does a wrong RADIUS shared secret look like?
The server can't verify the AP's Message-Authenticator, so it silently discards the requests. The AP retries and times out, the client never hears back, and the server log shows an invalid signature from the AP's address, or nothing at all.
Free for private and educational use. This interactive model is a simplified teaching aid and may contain mistakes. It is provided as is, without warranty. Use it to understand the concepts, not as a substitute for a site survey, vendor documentation or professional design advice.