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[Archive] Troubleshooting Layer 2/3 ISDN issues on J Series/SRX devices



Article ID: KB14616 KB Last Updated: 08 Oct 2020Version: 4.0
Commands to troubleshoot ISDN issues and sample working config

cli> show isdn status
Interface: br-2/0/1
Layer 1 status: up
Layer 2 status: down
CES: 0, Q.921: down, TEI: not assigned
CES: 1, Q.921: down, TEI: not assigned
Layer 3 status: 0 Active calls
Switch Type : NTDMS100
Interface Type : USER
T310 : 10 seconds
Tei Option : Power Up
CES: 0, SPID: 97364389410101
Endpoint state: Not Initialized
CES: 1, SPID: 97364369380101
Endpoint state: Not Initialized



#set system processes isdn-signaling traceoptions file isdnd.log
#set system processes isdn-signaling traceoptions flag all

#set interfaces br-x/x/x traceoptions flag all
#set interfaces br-x/x/x traceoptions file isdnd.log

start shell
su>>super user password

root>cty fpc 2               >> RE access to ISDN PIM, In this case, it is pim 2 (Interface:  br-2/0/1)

root>sh ifd brief         
This will give the index number for br interface.

PFPC2(uart)# sh ifd brief
Index Name Type Flags Slot State
----- -------------------- ----------- ------ ----- ------
0 .local. Local 0x0000000000000010 local Up
157 bc-2/0/1:1 HDLC 0x0000000000008004 2 Up
150 br-2/0/1 HDLC 0x0000000000008001 2 Harddown
152 br-2/0/2 HDLC 0x0000000000008001 2 Harddown
153 br-2/0/3 HDLC 0x0000000000008001 2 Harddown
156 dc-2/0/1 HDLC 0x0000000000008000 2 Up

PFPC2(uart)# sh ifd 150
Check for interface statistics on ifd interface using the index number.
Check for error counters and stats/alarms in the command output.

PFPC2(uart)# sh ifl brief
This will give index number for ifl (logical) interface for dc isdn-lapd interface.
use the index number in following command to get the status of the logical interface and incrementing counters.

Index Name Type Encapsulation Flags
----- -------------------- ------------- -------------- ------
0 .local..0 Unspecified Unspecified 0x0000000000000010
75 bc-2/0/1:1.0 PPP-Subordinate ??? (64) 0x0000000000000052
76 bc-2/0/1:2.0 PPP-Subordinate ??? (64) 0x0000000000000052
74 dc-2/0/1.32767 ISDN-LAPD ISDN-LAPD 0x0000000000000052

PFPC2(uart)# sh ifl 75

PFPC2(uart)# sh syslog messages

PFPC2(uart)# sh ifd summary


  1. Confirm that Layer 1 is up with the command show isdn status, and confirm that the correct ISDN PIM is in use. If Layer 1 is down, refer to KB14447 - ISDN layer 1 status shows down on J Series router.
  2. If the Layer 2 status is down, use the following traceoptions and commands for troubleshooting:
  3. Below is a sample working config for reference:
  4. interface {
    br-2/0/1 {
    description " ISDN Backup Circuit";
    traceoptions {
    flag all;
    isdn-options {
    switch-type ntdms100;
    calling-number 344420;
    dialer-options {
    pool 1 priority 3;
    dl0 {
    description "Dialer Interface for ISDN";
    traceoptions {
    flag all;
    hold-time up 60 down 60;
    encapsulation multilink-ppp;
    unit 0 {
    ppp-options {
    chap {
    access-profile ntest-01;
    local-name test-01;
    family inet {
    filter {
    dialer ISDN;
    address x.x.x.x/30;
    dialer-options {
    pool 1;
    dial-string 132222224;
    redial-delay 5;
    idle-timeout 600;
    load-threshold 75;
    firewall {

    dialer-filter ISDN {
    term ISDN-TRAFFIC {
    from {
    destination-address {
    then {
    access {
    profile test-01 {
    client test-02 chap-secret "password"; ## SECRET-DATA

Modification History:
 2020-10-04: Archive
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