We have a customer with multiple Grandstream GXW-4248 voice gateways that wants to use T.38 for sending and receiving faxes. They are running the most recent release (1.0.5.16). We have tested this successfully with other devices, including a Grandstream HT-702 and a Grandstream GXW-4004, but when configuring the Grandstream GXW-4248 the same way, the audio from the Grandstream to the fax machine cuts out at the renegotiation to T.38 and does not resume. When looking at a packet capture of the fax call, the Re-INVITE appears successful, but the first and only UDPTL packet sent by the Grandstream is reported as malformed by Wireshark: ITU-T Recommendation T.38 [Stream setup by SDP (frame 510)] [Stream frame: 510] [Stream Method: SDP] UDPTLPacket seq-number: 32768 primary-ifp-packet type-of-msg: t30-indicator (0) something unknown here [too long integer(per_normally_small_nonnegative_whole_number)] [Expert Info (Warn/Undecoded): something unknown here [too long integer(per_normally_small_nonnegative_whole_number)]] [something unknown here [too long integer(per_normally_small_nonnegative_whole_number)]] [Severity level: Warn] [Group: Undecoded] [Malformed Packet: T.38] [Expert Info (Error/Malformed): Malformed Packet (Exception occurred)] [Malformed Packet (Exception occurred)] [Severity level: Error] [Group: Malformed] Does anyone have any experience with trying to use T.38 with a Grandstream GXW-4248? Thanks, -- Nelson Hicks Network Operations SOCKET (573) 817-0000 ext. 210 nelsonh at socket.net