ISDN PRI Loopback Plug

[Anonymous]

I'm trying to bring up a SIP to PRI setup in the lab

I've setup my PRI and SIP trunks.

However, I am unable to bring up the D-Channel using a loopback plug. I am just receiving continues SABME messages

PIN 1 -> PIN 4

PIN 2 -> PIN 5

01:59:21.346 ISDN.L2_FMT PRI  1  ==============================================

01:59:21.346 ISDN.L2_FMT PRI  1  Sent  Sapi:00 C/R:C Tei:00 Ctl:SABME   P:1

01:59:21.351 ISDN.L2_FMT PRI  1  ==============================================

01:59:21.351 ISDN.L2_FMT PRI  1  Recd  Sapi:00 C/R:C Tei:00 Ctl:SABME   n 

01:59:22.345 ISDN.L2_FMT PRI  1  ==============================================

01:59:22.346 ISDN.L2_FMT PRI  1  Sent  Sapi:00 C/R:C Tei:00 Ctl:SABME   P:1

01:59:22.351 ISDN.L2_FMT PRI  1  ==============================================

01:59:22.351 ISDN.L2_FMT PRI  1  Recd  Sapi:00 C/R:C Tei:00 Ctl:SABME   P:

01:59:23.345 ISDN.L2_FMT PRI  1  ==============================================

01:59:23.346 ISDN.L2_FMT PRI  1  Sent  Sapi:00 C/R:C Tei:00 Ctl:SABME   P:1

01:59:23.350 ISDN.L2_FMT PRI  1  ==============================================

TA904#sho int t1 0/2

t1 0/2 is UP

  Receiver has no alarms

  T1 coding is B8ZS, framing is ESF

  FDL type is ANSI

  Line build-out is 0dB

  No remote loopbacks, No network loopbacks

  Acceptance of remote loopback requests enabled

  Tx Alarm Enable: rai

  Last clearing of counters 02:13:34

    loss of frame  : 9, last occurred 00:27:33

    loss of signal : 8, last occurred 00:27:32

    AIS alarm      : 1, last occurred 01:43:48

    Remote alarm   : 0

  DS0 Status: 123456789012345678901234

              XXXXXXXXXXXXXXXXXXXXXXXX

  Status Legend: '-' = DS0 is not allocated

                 'X' = DS0 is allocated (nailed)

  Signaling Bit Status: 123456789012345678901234

                   RxA: 100100001001000000000000

                   RxB: 010000000100010000000000

                   TxA: 010001000000100100001001

                   TxB: 010001000000010000000100

                        123456789012345678901234

  Line Status: -- No Alarms --

  5 minute input rate 0 bits/sec, 0 packets/sec

  5 minute output rate 0 bits/sec, 0 packets/sec

  Current Performance Statistics:

    0 Errored Seconds, 0 Bursty Errored Seconds

    0 Severely Errored Seconds, 0 Severely Errored Frame Seconds

    0 Unavailable Seconds, 0 Path Code Violations

    0 Line Code Violations, 0 Controlled Slip Seconds

    0 Line Errored Seconds, 0 Degraded Minutes

  TDM group 1, line protocol is not set

    Encapsulation is not set

TA904#show interfaces pri 1

pri 1 is DOWN

  Switch protocol:  National ISDN 2

  Signaling role:  network (NT) b-channel-restarts enabled

  Ringing signal:  calling TE provides audible ringing

  Calling-party override:  disabled

  Calling-party presentation:  allowed

  Calling-party number:  (no number configured)

  digits transferred all

  ISDN name-delivery:  via Facility msg following Proceeding msg

  progress indicator #8 in alerting message:  enabled

  progress indicator #2 in connect message:  disabled

  progress indicator #1 in setup message:  disabled

  progress indicator #3 in setup message:  disabled

  progress indicator location:  public

  resource-selection: circular descending

  TBCT:  disabled

  area code: 

  Transmission of redirecting numbers is enabled

  Redirecting numbers: sent as received

  Connected interface: t1 0/2 tdm-group 1

  Channel status 123456789012345678901234

                 ........................

    Legend: - = Unallocated        . = Inactive

            A = Active B channel   B = Backup D channel

            D = Active D channel   M = Maintenance

            R = Restart

    2206 packets input, 6618 bytes, 0 no buffer

    0 runts, 6 giants, 0 throttles

    21 input errors, 9 CRC, 1 frame

    11 abort, 0 discards, 0 overruns

    2536 packets output, 7608 bytes, 0 underruns

Configuration

interface t1 0/2

  tdm-group 1 timeslots 1-24 speed 64

  no shutdown

!

!

interface pri 1

  isdn name-delivery proceeding

  connect t1 0/2 tdm-group 1

  role network b-channel-restarts enable

  no shutdown

!

!

isdn-group 1

  connect pri 1

!

!

!

!

timing-source t1 0/2

!

timing-source internal secondary

!      

!

voice feature-mode network

voice forward-mode network

!

!

!

voice trunk T01 type sip

  sip-server primary **HIDDEN**

  registrar primary **HIDDEN**

  registrar expire-time 0

!

voice trunk T02 type isdn

  description "PRI"

  resource-selection circular descending

  connect isdn-group 1

  rtp delay-mode adaptive

!

!

voice grouped-trunk SIP

  trunk T01

  accept $ cost 0

!

!

voice grouped-trunk PRI

  trunk T02

  accept $ cost 0

Am I missing something?

T1 and PRI's are new to me, bringing it into the lab to understand them better.

Thanks!

[jayh · Accepted solution]

You will not be able to bring up a PRI with a loopback plug. The underlying T1 will come up but not the PRI.

PRI connections have one end configured for role network and the other for role user. The loopback plug will echo back the configuration applied to the interface. so if your TA900 is set to role user it will reflect two user devices communicating with each other or if it is set to network, two network devices connected together. This is not a valid combination and the PRI will not come up.

If you have two TA900 devices you can configure one of them as network and the other as user and they'll work fine.

It may be possible to configure two PRIs on the same box for testing with one as role user and one as network just to see the PRI go active. I haven't tried this but it should be possible to at least get the D-channel up.

As with any T1 connection, pay attention to clocking. One T1 needs to source the clock and the other sync to the received clock on the T1.

[Anonymous]

Thanks for that,

I have another TA904 and will set that up for network!