los errores los saque de el log del cliente asi:
[2013-11-22 14:40:13] ERROR[15962] chan_dahdi.c: MFC/R2 protocol error on chan 2: Invalid CAS
[2013-11-22 14:40:13] ERROR[15962] chan_dahdi.c: Chan 3 - Protocol error. Reason = Invalid CAS, R2 State = Seize ACK Transmitted, MF state = Seize ACK Transmitted, MF Group = Backward MF init, CAS = 0x0C
[2013-11-22 14:40:13] ERROR[15962] chan_dahdi.c: MFC/R2 protocol error on chan 3: Invalid CAS
[2013-11-22 14:40:13] ERROR[15962] chan_dahdi.c: Chan 4 - Protocol error. Reason = Invalid CAS, R2 State = Seize ACK Transmitted, MF state = Seize ACK Transmitted, MF Group = Backward MF init, CAS = 0x0C
[2013-11-22 14:40:13] ERROR[15962] chan_dahdi.c: MFC/R2 protocol error on chan 4: Invalid CAS
[2013-11-22 14:40:13] ERROR[15962] chan_dahdi.c: Chan 5 - Protocol error. Reason = Invalid CAS, R2 State = Seize ACK Transmitted, MF state = Seize ACK Transmitted, MF Group = Backward MF init, CAS = 0x0C
[2013-11-22 14:40:13] ERROR[15962] chan_dahdi.c: MFC/R2 protocol error on chan 5: Invalid CAS
[2013-11-22 14:40:13] ERROR[15962] chan_dahdi.c: Chan 6 - Protocol error. Reason = Invalid CAS, R2 State = Seize ACK Transmitted, MF state = Seize ACK Transmitted, MF Group = Backward MF init, CAS = 0x0C
[2013-11-22 14:40:13] ERROR[15962] chan_dahdi.c: MFC/R2 protocol error on chan 6: Invalid CAS
[2013-11-22 14:40:13] ERROR[15962] chan_dahdi.c: Chan 7 - Protocol error. Reason = Invalid CAS, R2 State = Seize ACK Transmitted, MF state = Seize ACK Transmitted, MF Group = Backward MF init, CAS = 0x0C
[2013-11-22 14:40:13] ERROR[15962] chan_dahdi.c: MFC/R2 protocol error on chan 7: Invalid CAS
[2013-11-22 14:40:13] ERROR[15962] chan_dahdi.c: Chan 8 - Protocol error. Reason = Invalid CAS, R2 State = Seize ACK Transmitted, MF state = Seize ACK Transmitted, MF Group = Backward MF init, CAS = 0x0C
[2013-11-22 14:40:13] ERROR[15962] chan_dahdi.c: MFC/R2 protocol error on chan 8: Invalid CAS
[2013-11-22 14:40:13] ERROR[15962] chan_dahdi.c: Chan 9 - Protocol error. Reason = Invalid CAS, R2 State = Seize ACK Transmitted, MF state = Seize ACK Transmitted, MF Group = Backward MF init, CAS = 0x0C
[2013-11-22 14:40:13] ERROR[15962] chan_dahdi.c: MFC/R2 protocol error on chan 9: Invalid CAS
[2013-11-22 14:40:13] ERROR[15962] chan_dahdi.c: Chan 10 - Protocol error. Reason = Invalid CAS, R2 State = Seize ACK Transmitted, MF state = Seize ACK Transmitted, MF Group = Backward MF init, CAS = 0x0C
[2013-11-22 14:40:13] ERROR[15962] chan_dahdi.c: MFC/R2 protocol error on chan 10: Invalid CAS
[2013-11-22 23:21:03] ERROR[17367] chan_dahdi.c: Chan 1 - Protocol error. Reason = Forward Safety Timeout, R2 State = Seize ACK Received, MF state = Waiting Far End Timeout, MF Group = Forward Group I, CAS = 0x0C
[2013-11-23 23:22:40] ERROR[21131] chan_dahdi.c: Chan 1 - Protocol error. Reason = Forward Safety Timeout, R2 State = Seize ACK Received, MF state = Waiting Far End Timeout, MF Group = Forward Group I, CAS = 0x0C
[2013-11-23 23:23:26] ERROR[21135] chan_dahdi.c: Chan 1 - Protocol error. Reason = Forward Safety Timeout, R2 State = Seize ACK Received, MF state = Waiting Far End Timeout, MF Group = Forward Group I, CAS = 0x0C
[2013-11-25 11:35:01] ERROR[15962] chan_dahdi.c: Chan 8 - Protocol error. Reason = Multi Frequency Cycle Timeout, R2 State = Seize ACK Transmitted, MF state = ANI Request Transmitted, MF Group = Backward Group C, CAS = 0x00
[2013-11-25 13:30:46] ERROR[4730] chan_dahdi.c: Chan 2 - Protocol error. Reason = Forward Safety Timeout, R2 State = Seize ACK Received, MF state = Waiting Far End Timeout, MF Group = Forward Group I, CAS = 0x0C
[2013-11-25 19:48:26] ERROR[15962] chan_dahdi.c: Chan 5 - Protocol error. Reason = Multi Frequency Cycle Timeout, R2 State = Seize ACK Transmitted, MF state = ANI Request Transmitted, MF Group = Backward Group C, CAS = 0x00
[2013-11-27 20:05:20] ERROR[16070] chan_dahdi.c: Chan 1 - Protocol error. Reason = Invalid CAS, R2 State = Seize ACK Transmitted, MF state = Seize ACK Transmitted, MF Group = Backward MF init, CAS = 0x0C
[2013-11-27 20:05:20] ERROR[16070] chan_dahdi.c: MFC/R2 protocol error on chan 1: Invalid CAS
[2013-11-27 20:05:20] ERROR[16070] chan_dahdi.c: Chan 2 - Protocol error. Reason = Invalid CAS, R2 State = Seize ACK Transmitted, MF state = Seize ACK Transmitted, MF Group = Backward MF init, CAS = 0x0C
[2013-11-27 20:05:20] ERROR[16070] chan_dahdi.c: MFC/R2 protocol error on chan 2: Invalid CAS
[2013-11-27 20:05:20] ERROR[16070] chan_dahdi.c: Chan 3 - Protocol error. Reason = Invalid CAS, R2 State = Seize ACK Transmitted, MF state = Seize ACK Transmitted, MF Group = Backward MF init, CAS = 0x0C
[2013-11-27 20:05:20] ERROR[16070] chan_dahdi.c: MFC/R2 protocol error on chan 3: Invalid CAS
[2013-11-27 20:05:20] ERROR[16070] chan_dahdi.c: Chan 4 - Protocol error. Reason = Invalid CAS, R2 State = Seize ACK Transmitted, MF state = Seize ACK Transmitted, MF Group = Backward MF init, CAS = 0x0C
[2013-11-27 20:05:20] ERROR[16070] chan_dahdi.c: MFC/R2 protocol error on chan 4: Invalid CAS
[2013-11-27 20:05:20] ERROR[16070] chan_dahdi.c: Chan 5 - Protocol error. Reason = Invalid CAS, R2 State = Seize ACK Transmitted, MF state = Seize ACK Transmitted, MF Group = Backward MF init, CAS = 0x0C
[2013-11-27 20:05:20] ERROR[16070] chan_dahdi.c: MFC/R2 protocol error on chan 5: Invalid CAS
[2013-11-27 20:05:20] ERROR[16070] chan_dahdi.c: Chan 6 - Protocol error. Reason = Invalid CAS, R2 State = Seize ACK Transmitted, MF state = Seize ACK Transmitted, MF Group = Backward MF init, CAS = 0x0C
[2013-11-27 20:05:20] ERROR[16070] chan_dahdi.c: MFC/R2 protocol error on chan 6: Invalid CAS
[2013-11-27 20:05:20] ERROR[16070] chan_dahdi.c: Chan 7 - Protocol error. Reason = Invalid CAS, R2 State = Seize ACK Transmitted, MF state = Seize ACK Transmitted, MF Group = Backward MF init, CAS = 0x0C
[2013-11-27 20:05:20] ERROR[16070] chan_dahdi.c: MFC/R2 protocol error on chan 7: Invalid CAS
[2013-11-27 20:05:20] ERROR[16070] chan_dahdi.c: Chan 8 - Protocol error. Reason = Invalid CAS, R2 State = Seize ACK Transmitted, MF state = Seize ACK Transmitted, MF Group = Backward MF init, CAS = 0x0C
[2013-11-27 20:05:20] ERROR[16070] chan_dahdi.c: MFC/R2 protocol error on chan 8: Invalid CAS
[2013-11-27 22:27:29] ERROR[16269] chan_dahdi.c: Chan 4 - Protocol error. Reason = Invalid CAS, R2 State = Idle, MF state = MF Engine Off, MF Group = No Group, CAS = 0x04
[2013-11-27 22:27:29] ERROR[16269] chan_dahdi.c: MFC/R2 protocol error on chan 4: Invalid CAS
[2013-11-27 22:27:29] ERROR[16269] chan_dahdi.c: Chan 8 - Protocol error. Reason = Invalid CAS, R2 State = Idle, MF state = MF Engine Off, MF Group = No Group, CAS = 0x04
[2013-11-27 22:27:29] ERROR[16269] chan_dahdi.c: MFC/R2 protocol error on chan 8: Invalid CAS
[2013-11-27 22:53:04] ERROR[16269] chan_dahdi.c: Chan 1 - Protocol error. Reason = Invalid CAS, R2 State = Clear Forward Transmitted, MF state = MF Engine Off, MF Group = Forward Group II, CAS = 0x04
[2013-11-27 22:53:04] ERROR[16269] chan_dahdi.c: MFC/R2 protocol error on chan 1: Invalid CAS
[2013-11-29 09:39:47] ERROR[30116] chan_dahdi.c: Chan 2 - Protocol error. Reason = Forward Safety Timeout, R2 State = Seize ACK Received, MF state = Waiting Far End Timeout, MF Group = Forward Group I, CAS = 0x0C
[2013-11-29 09:43:55] ERROR[30195] chan_dahdi.c: Chan 2 - Protocol error. Reason = Forward Safety Timeout, R2 State = Seize ACK Received, MF state = Waiting Far End Timeout, MF Group = Forward Group I, CAS = 0x0C
[2013-11-30 15:02:25] ERROR[25616] chan_dahdi.c: Chan 1 - Protocol error. Reason = Forward Safety Timeout, R2 State = Seize ACK Received, MF state = Waiting Far End Timeout, MF Group = Forward Group I, CAS = 0x0C
[2013-11-30 15:03:01] ERROR[25623] chan_dahdi.c: Chan 1 - Protocol error. Reason = Forward Safety Timeout, R2 State = Seize ACK Received, MF state = Waiting Far End Timeout, MF Group = Forward Group I, CAS = 0x0C
[root@localhost scripts]# asterisk -vvvvvvvvr
Verbosity is at least 11
localhost*CLI> mfcr2 show channels
Chan Variant Max ANI Max DNIS ANI First Immediate Accept Tx CAS Rx CAS
1 MX 10 4 No No IDLE IDLE
2 MX 10 4 No No IDLE IDLE
3 MX 10 4 No No IDLE IDLE
4 MX 10 4 No No IDLE IDLE
5 MX 10 4 No No IDLE IDLE
6 MX 10 4 No No IDLE IDLE
7 MX 10 4 No No IDLE IDLE
8 MX 10 4 No No IDLE IDLE
9 MX 10 4 No No IDLE IDLE
10 MX 10 4 No No IDLE IDLE
localhost*CLI>
cuando genera error en el CAS en vez de IDLE me marca: block o los 0x00 y cosas asi, por eso decidi usar el grep