I'm working with a third-party app that authenticates to a FreeRADIUS server via MSCHAPv2 over PEAP and need up update a few parts of it, but I can't figure out what FreeRADIUS is sending over the PEAP tunnel when it's not sending MSCHAPv2 data. The current code doesn't try and break down the messages, possibly because my predecessor also couldn't figure out what they were, but there's now a requirement to do this. The initial Identity Request sent by FreeRADIUS over the PEAP tunnel is: 01 // Identity-Request 06 // ? 00 05 // length = 5 01 // ? The Identity Request sent by FreeRADIUS over the PEAP tunnel in response to an incorrect identity in the MSCHAPv2 process, i.e. what you get instead of an MSCHAPv2 response, is: 01 // Identity-Request 08 // ? 00 0B // length = 11 21 80 03 00 02 00 02 // ? Problem is I can't translate these messages into anything useful (the field names I've used above are guesswork), this doesn't correspond to any message format that I can identify, RADIUS, EAP, DIAMETER, PEAP, there are bits and pieces in there that could correspond to various things like EAP and RADIUS, and the byte string starting 0x21 could be a MS-Authentication-TLV but what follows doesn't match draft-hiller-eap-tlv-01.txt, and it also doesn't work as an EAP-Request, also 0x21. Can anyone tell me what format this is? JG.