Showing results for 
Search instead for 
Did you mean: 

E1 PRI D-Channel Problem



we got a problem with the E1 interface in our router, the ISDN D-Channel is not comming up.

The status of the L2 on the "sh isdn status" command is flapping between "AWAITING_ESTABLISHMENT" and TEI_ASSIGNED".

We are running IOS 12.4(9)T1 on a Cisco 3660.

Details (and if we think this is correct):

- ISDN-Switch: primary-net5 - ok

- prigroup timeslots 1-31 - ok

- int serial 1/0:15, encapsulation hdlc - ok

- Controller e1 is up, no local or remote alarms - ok (no L1 problem)

- sh isdn status L1 ACTIVE - ok


- sh isdn service -

ISDN Se1/0:15, Channel [1-31]

Configured Isdn Interface (dsl) 0

Channel State (0=Idle 1=Proposed 2=Busy 3=Reserved 4=Restart 5=Maint_Pend)

Channel : 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1

State : 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 3 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

Service State (0=Inservice 1=Maint 2=Outofservice 8=MaintPend 9=OOSPend)

Channel : 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1

State : 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 - not ok

- debug isdn q921 - ISDN Se1/0:15 Q921: User TX -> SABMEp sapi=0 tei=0

ISDN Se1/0:15 Q921: User TX -> SABMEp sapi=0 tei=0 - not ok (No answer from the network site)

- debug isdn mgmnt - ISDN Se1/0:15 MGMNT: CM_MDL_ERR_IND: error G skip idverify 0 switch type 18 - not ok

What we have done:

- We checked all physical connection, all ok.

- We searched in the Bug-Toolkit, but don't found someting like our problem in detail.

- We contacted the Telco (German Telekom). They checked the line (at oure site), they got no problem with L2 or L3 communication and their Test -Equipment. They did a L2-Trace and we could see that there were SABME-Messages from the ISDN-Switch, which are not seen in the q921 debug output from the router, but we saw broken U/I-Frames from the router in the L2-Trace.

- We reloaded teh router - the same problem.

What could we do now?

Thank you,

Sebastian Krueger

11 Replies 11

paolo bevilacqua
Hall of Fame Master Hall of Fame Master
Hall of Fame Master

Please send show "controllers e1" to begin with.

Are you positive about CRC4/ no CRC4 settings on the circuit?

Also please describe exactly what cable are you using from router to telco device. If a regular ethernet patch, that is NOT right.


thank you for your reply. Here the output from "sh controllers E1":

E1 1/0 is up.

Applique type is Channelized E1 - balanced


No alarms detected.

alarm-trigger is not set

Framing is CRC4, Line Code is HDB3, Clock Source is Line.

Data in current interval (792 seconds elapsed):

0 Line Code Violations, 0 Path Code Violations

0 Slip Secs, 0 Fr Loss Secs, 0 Line Err Secs, 0 Degraded Mins

0 Errored Secs, 0 Bursty Err Secs, 0 Severely Err Secs, 0 Unavail Secs

Total Data (last 24 hours)

0 Line Code Violations, 0 Path Code Violations,

0 Slip Secs, 0 Fr Loss Secs, 0 Line Err Secs, 0 Degraded Mins,

0 Errored Secs, 0 Bursty Err Secs, 0 Severely Err Secs, 0 Unavail Secs

The CRC4-Framing is correctly set, as shown above.

We use an original Cisco-cable (DB15 to RJ45). The layout is:


DB15-2 to RJ45-5 and DB15-9 to RJ45-4


Db15-8 to RJ45-1 and DB15-15 to RJ45-2

That should be correct.



Everything is correct. Matter is, you receive no data, and telco receive corrupt data.

Try this, configure "loopback line" under controller E1. Ask telco to trace L2 again. they should seen their very own q921 frames. If they do, problem is with router. If the don't, problem is with the circuit.

Alternative to this, would be a loopback plug either rj45 or db-15, instead of software-commanded loopback.

just check by changing the framing to no CRC4

as it is generally enabled at telco.

oscar cordero


We have the same erros that you describe in:

Please tell me how you fix this.

4 years old thread, unlikely to get an answer from am "ask and forget" OP..

oscar cordero
We are working with new generation routers and PRI cards, for the router "2900 series" and card PRI "VWIC3". This newest equipment have not reported till now any BUG about compatibility with Switchs ISDN providers.

Today We upgrade the IOS from c2900-universalk9-mz.SPA.151-3.T1.bin to c2900-universalk9-mz.SPA.152-2.T.bin and this solve this issue.

So in conclution from the beginner the configuration in boths sides (provider Gib Telecom and Our Cisco router- CUCM) was ok. The issue was the firmware router!!!.

cisco is reporting this BUG.

So, the fault is with Cisco, but you low rate my post made to help ?

oscar cordero

Sorry I dont understand the way to rate the posts.  The total is the promedium of all? so is better just rate one post with maximum calification that rate many low rate?. I really apreciate the help that people give me in this forum.

Yes, ratings are averaged, but don't worry about that.

Thanks and good luck!

Claudio Costa


Hi Sebastian,

I've been having as same problem as you. Did you already fix that? Has any news about it?




Warm Regards,

Cláudio Costa

Getting Started

Find answers to your questions by entering keywords or phrases in the Search bar above. New here? Use these resources to familiarize yourself with the community:

Recognize Your Peers