One thing I learnt from my senior friend here Paolo, is to use the loopback command on your controller...This way you can authoritatively inform the telco that your end is fine..to use the loopback command do the following:

1. conf t

2. controller t1 0/3/0

3.loopback local line

Exit the config mode and type sh controller t1 0/3/0, you should see up up and looped.

Coommon and most helpful commands used to troubleshoot isdn setup are

1. debug isdn q.921 ..if your layer 2 is not coming up, this will help you to see message exchanges between your t1 card and the telco switch

2. Use show isdn status, to see the status of your isdn cirtcuit, this will show layer1 to layer 3 status..ideally if evrything is good, you should see multiple frame established..similar to this

ksh1f-intr3825#sh isdn status

Global ISDN Switchtype = primary-net5

ISDN Serial1/0/0:15 interface

dsl 0, interface ISDN Switchtype = primary-net5

Layer 1 Status:

ACTIVE

Layer 2 Status:

TEI = 0, Ces = 1, SAPI = 0, State = MULTIPLE_FRAME_ESTABLISHED

Layer 3 Status:

1 Active Layer 3 Call(s)

CCB:callid=479A, sapi=0, ces=0, B-chan=1, calltype=VOICE

Active dsl 0 CCBs = 1

The Free Channel Mask: 0x80007FFE

Number of L2 Discards = 0, L2 Session ID = 4

Total Allocated ISDN CCBs = 1

ksh1f-intr3825#

3. You can use a show controller t1 0/3/0 to see if there are any alarms on your circuit..The type of alarm will tell you where the problem is.

Attached is a glossary of isdn alarms and what they mean.

4. You might need to add this command under your

interface Serial0/3/0:23

isdn bchan-number-order ascending.

This is used to avoid a term called glare condition..basically this happen when your telco and router select channels in same order.

5. ALso on your pots dial-peer you will need to add

progress_ind alert enable 8

eg dial-p 1 voice pots

progress_ind alert enable 8

This will let your users hear phone ringing before the called party picksup.

This is all I can think of now...