2 Replies Latest reply on Oct 30, 2017 10:09 AM by ajr3v

ISDN PRI Loopback Plug

ajr3v Oct 27, 2017 4:01 PM

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!

Re: ISDN PRI Loopback Plug

jayh Oct 30, 2017 10:05 AM (in response to ajr3v)

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.
Like Show 0 Likes(0)

Actions
- Re: ISDN PRI Loopback Plug
  
  ajr3v Oct 30, 2017 10:09 AM (in response to jayh)
  
  Thanks for that,
  I have another TA904 and will set that up for network!
  
  Like Show 0 Likes(0)
  
  Actions

Go to original post