No connection on a cisco 3660 router with an E1 line

[oblivionvlad]

I have a 3660 router with a E1 R2-digital signaling line, an ethernet connection to the local lan and 30 mica modems. I tried to set it up for dialin access from remote user and all I get when dialing in is a fast busy tone (or number not allocated as I found out). The telco says that the line is ok and that I should allocate the numbers they gave me on my side ( I didn't find any way to do such a thing on the router). I tried to dial out with telnet and ATDT from one of them mica modems instead and got this log:

1w6d: Modem 2/1 CSM: Called Number Rcvd = 2088800

1w6d: Modem 2/1 CSM: (CSM_PROC_IDLE)<--MODEM_DIAL_OUT

1w6d: Modem 2/1 Mica: received dialstring 2088800

1w6d: Modem 2/1 CSM: received EVENT_CHANNEL_LOCK with call_id 0005

1w6d: src 1/0/4 dest 2/0/1 cause 769

1w6d: Modem 2/1 CSM: (CSM_PROC_OC_CAS_PENDING_CHANNEL_LOCK)<--DSX0_BCHAN_ASSIGNED

1w6d: Modem 2/1 Mica: configured for Originate mode, with Upper R2 signaling, 0x0 tone detection.

1w6d: Message from Trunk E1 (1): (0/4): TX SEIZURE (ABCD=0001)

1w6d: Modem 2/1 Mica: in modem state CALL_SETUP

1w6d: Message from Trunk E1 (1): (0/4): TX IDLE (ABCD=1001)

1w6d: Modem 2/1 Mica: in modem state TERMINATING

1w6d: Modem 2/1 CSM: (CSM_PROC_OC_CAS_WAITING_FOR_TONE)<--MODEM_DISCONNECTED

1w6d: Modem 2/1 Mica: in modem state IDLE

1w6d: Modem 2/1 CSM: (CSM_PROC_OC_CAS_WAITING_FOR_TONE)<--QUEUED_DISCONNECT

1w6d: Modem 2/1 CSM: CSM_MODEM_DEALLOCATE: modem is deallocated

1w6d: Modem 2/1 Mica: DISCONNECT after 00:00:00, due to reason (0x6007) AT mode command abort.

It seem that te call request gets to the E1 module but a connection cannot be established. I don't know exactly what that ABCD means although I read some theory on the R2-signaling. I think there my be something related the cas-custom settings but, as the telco didn't tell anything about specific options (just the ds0-group part), I used the following:

ds0-group 0 timeslots 1-15,17-31 type r2-digital r2-compelled ani

cas-custom

country east-europe

If anyone has any remote ideeas please share. I've been banging my head against the nearest wall for a while now.

I also get something about interface Gr0, Gr0 flag set when I issue the show debug command. I don't know exactly what it means.

[mheusinger]

Hi,

are you sure that the CAS is working correct on the E1? ABCD Bits are the digital representation of analog 4 signaling lines. In short: there has to be a certain sequence of these 4 bits to signal call setup, number dialed and the like. Unfortunately there are many different ways implemented of what ABCD Bits are signaling the different states.

Can you get hold on some documentation what ABCD=0001 and ABCD=1001 is used for?

regards

Martin

[oblivionvlad]

Thank you for the reply. My guess was that there is something about the cas-custom setting also.

I checked the ABCD meaning and found this:

C and D bits are not usually used and are set on 0,1. A=1 B=0 means idle. Then we have the following transitions:

Forward Seizure A,B: 1,0 to 0,0

Forward Clear-forward A,B: 0,0 to 1,0

Backward Seizure Acknowledgment (ACK) A,B: 1,0 to 1,1

Backward Answer A,B: 1,1 to 0,1

Backward Clear-back A,B: 0,1 to 1,1

Backward Release-guard A,B: 0,1 to 1,0

So it seems the modem tries to get the line (ABCD=0001) but nothing happend aftewards (hence the TX IDLE part with ABCD=1001).

In the cisco documentation I also found a correct sequence and that is:

Oct 29 15:59:46.544: Mica Modem(1/59): Call Setup

Oct 29 15:59:46.544: from Trunk(0): (1/25): Tx SEIZURE (ABCD=0001)

Oct 29 15:59:46.616: Mica Modem(1/59): State Transition to Call Setup

Oct 29 15:59:46.712: from Trunk(0): (1/25): Rx SEIZURE_ACK (ABCD=1101)

So I don't get the SEIZURE_ACK.

Some settings that got my attention are:

Router(config-ctrl-cas)# answer-signal

Router(config-ctrl-cas)# category

Router(config-ctrl-cas)# invert-abcd

Router(config-ctrl-cas)# ka

Router(config-ctrl-cas)# kd

Router(config-ctrl-cas)# metering

Router(config-ctrl-cas)# nc-congestion

Router(config-ctrl-cas)# unused-abcd

Router(config-ctrl-cas)# request-category

They require certain parameters related to r2 signaling that I guess the telco should know.

I tried the invert-abcd and unused-abcd commands in the cas-custom commands and set all the possible 16 combinations but i get the same log. Is there some important setting from cas-custom that is usually modified by a telco and that I should ask about?

Thanks.