Posted by: Mudassir Ali | February 3, 2012

Troubleshooting ISDN Voice Calls

Troubleshooting ISDN Voice Calls
Troubleshooting call starts at the bottom and works its way up. The general flow of reasoning looks for the following:

  1. Do we see the call arrive? (A yes answer advances to the next question)
  2. Does the receiving end answer the call?
  3. Does the call complete?
  4. Is data passing across the link?
  5. Is the session established? (PPP or terminal)

For calls involving digital modems, first make sure the underlying ISDN or CAS is receiving the call.
Troubleshooting and Debugging VoIP Call Basics
Router Call Flow Telephony Interface Architecture

Troubleshooting Voice Calls

Show isdn status

This show isdn status output is an example of a properly functioning BRI circuit. In this example, Layer 1 is Active, the Terminal Endpoint Identifiers (TEIs) are successfully negotiated, and ISDN Layer 3 (end-to-end) is ready to make or receive calls

Good Bad
Router#show isdn status
The current
ISDN Switchtype
= basic-ni1
ISDN BRI0 interface
Layer 1
Status:
ACTIVE
Layer 2
Status:
TEI = 109, State = MULTIPLE_FRAME_ESTABLISHED
TEI = 110, State = MULTIPLE_FRAME_ESTABLISHED
Spid Status:
TEI 109, ces = 1, state = 8(established)
spid1 configured, spid1 sent, spid1 valid
Endpoint ID Info: epsf = 0, usid = 1, tid = 1
TEI 110, ces = 2, state = 8(established)
spid2 configured, spid2 sent, spid2 valid
Endpoint ID Info: epsf = 0, usid = 3, tid = 1
Layer 3 Status:
0 Active Layer 3 Call(s)
Activated dsl 0 CCBs = 0
Total Allocated ISDN CCBs = 0
Router#show isdn status
Global ISDN Switchtype = basic-ni
ISDN BRI0 interface dsl 0, interface ISDN Switchtype = basic-ni
Layer 1 Status:
DEACTIVATED !— Layer 1 is down.
Layer 2 Status:
Layer 2 NOT Activated !— Layer 2 is down
Spid Status:
TEI Not Assigned, ces = 1, state = 3(await establishment)
spid1 configured, spid1 NOT sent, spid1 NOT valid
TEI Not Assigned, ces = 2, state = 1(terminal down)
spid2 configured, spid2 NOT sent, spid2 NOT valid
Layer 3 Status:
0 Active Layer 3 Call(s)
Activated dsl 0 CCBs = 0
The Free Channel Mask: 0x80000003
Total Allocated ISDN CCBs = 0
superchicken#

Troubleshooting PRI Setup
1. Show isdn status
2. Verify whether Layer 1 is in the ACTIVE state. The status of Layer 1 must always be ACTIVE unless the T1 is down. Do a shut, no shut on the controller.
3. Ensure that Layer 2 is in the MULTIPLE_FRAME_ESTABLISHED state. Use the debug isdn q921 Command to troubleshoot.

Cisco IOS Debug Command Reference

debug isdn q921 (Layer 2)
debug isdn q931 (Layer 3)
debug voip ccapi inout

Cisco IOS Voice Troubleshooting and Monitoring — H.323 Gateway Troubleshooting
Verifying Digits Received and Sent on the POTS Call Leg
· show dialplan number-This command is used to show which dial peer is reached when a particular telephone number is dialed.
· debug vtsp session-This command displays information on how each network indication and application request is processed, signaling indications, and DSP control messages.
· debug vtsp dsp -This command displays the digits as they are received by the voice-port.
Verifying End-to-End VoIP Signaling on the VoIP Call Leg
debug voip ccapi inout: Look for incoming dial-peer, outgoing dial-peer, (tag)
debug isdn q931: Look for calling party, called party number and cause code.
The debug ISDN Q931 and debug voip ccapi inout commands have been enabled. Some of the debugs were omitted for clarity.

debug voip ccapi inout
Good Bad
Router#
*Mar 2 21:36:10.132: ISDN Se3/0:15: RX <- SETUP pd = 8 callref = 0x0024
*Mar 2 21:36:10.136: Bearer Capability i = 0x8090A3
*Mar 2 21:36:10.136: Channel ID i = 0xA98386
*Mar 2 21:36:10.136: Facility i = 0x91AA068001008201008B0102A114020262A
002013B300B30090A01050A01030A0104
*Mar 2 21:36:10.140: Facility i = 0x91AA068001008201008B0100A10C020262B
006042B0C09008400
*Mar 2 21:36:10.140: Calling Party Number i = 0x00, 0x83, ‘5000’,
Plan:Unknown, Type:Unknown
*Mar 2 21:36:10.144: Called Party Number i = 0x80, ‘5’, Plan:Unknown,
Type:Unknown
*Mar 2 21:36:10.144: High Layer Compat i = 0x9181
!— An incoming call with the first digit of called number 5.
*Mar 2 21:36:10.164: ISDN Se3/0:15: TX -> SETUP_ACK pd = 8 callref = 0x8024
*Mar 2 21:36:10.164: Channel ID i = 0xA98386
*Mar 2 21:36:10.360: ISDN Se3/0:15: RX <- INFORMATION pd = 8 callref = 0x0024
*Mar 2 21:36:10.364: Called Party Number i = 0x80, ‘6’, Plan:Unknown,
Type:Unknown
!— An information message with the next digit 6.
*Mar 2 21:36:10.660: ISDN Se3/0:15: RX <- INFORMATION pd = 8 callref = 0x0024
*Mar 2 21:36:10.664: Called Party Number i = 0x80, ‘7’, Plan:Unknown,
Type:Unknown
!— An information message with the next digit 7.
*Mar 2 21:36:10.924: ISDN Se3/0:15: RX <- INFORMATION pd = 8 callref = 0x0024
*Mar 2 21:36:10.924: Called Party Number i = 0x80, ‘8’, Plan:Unknown,
Type:Unknown
!— An information message with the next digit 8.
*Mar 2 21:36:20.168: ccCallSetupRequest encapType 2 clid_restrict_disable 1
null_orig_clg 0 clid_transparent 0 callingNumber 5000
*Mar 2 21:36:20.172: dest pattern 5T, called 5678, digit_strip 0
*Mar 2 21:36:20.172: callingNumber=5000, calledNumber=5678, redirectNumber=
display_info= calling_oct3a=83
!— The router matches received digits 5678 with dial peer 1.
*Mar 2 21:36:20.228: ISDN Se3/0:15: TX -> CALL_PROC pd = 8 callref = 0x8024
*Mar 2 21:36:20.420: cc_api_call_cut_progress(vdbPtr=0x6221F1E8, callID=0x38,
prog_ind=0x8, sig_ind=0x1)
*Mar 2 21:36:20.440: ISDN Se3/0:15: TX -> ALERTING pd = 8 callref = 0x8024
*Mar 2 21:36:20.440: Progress Ind i = 0x8188 – In-band info or appropriate
now available
!— The call is successfully routed and the remote phone is ringing.
Router#
Router#
*Mar 2 01:47:05.705: ISDN Se3/0:15: RX <- SETUP pd = 8 callref = 0x001A
*Mar 2 01:47:05.705: Bearer Capability i = 0x8090A3
*Mar 2 01:47:05.709: Channel ID i = 0xA9839B
*Mar 2 01:47:05.709: Facility i = 0x91AA068001008201008B0102A11
402025CA002013B300B30090A01050A01030A0104
*Mar 2 01:47:05.713: Facility i = 0x91AA068001008201008B0100A10
C02025CB006042B0C09008400
*Mar 2 01:47:05.713: Calling Party Number i = 0x00, 0x83, ‘5000’,
Plan:Unknown, Type:Unknown
*Mar 2 01:47:05.717: Called Party Number i = 0x80, ‘5’, Plan:Unknown,
Type:Unknown
*Mar 2 01:47:05.717: High Layer Compat i = 0x9181
!— An incoming call with the first digit of called number 5.
*Mar 2 01:47:05.729: ISDN Se3/0:15: TX -> SETUP_ACK pd = 8 callref = 0x801A
*Mar 2 01:47:05.729: Channel ID i = 0xA9839B
*Mar 2 01:47:06.385: ISDN Se3/0:15: RX <- INFORMATION pd = 8 callref = 0x001A
*Mar 2 01:47:06.385: Called Party Number i = 0x80, ‘5’, Plan:Unknown,
Type:Unknown
!— An information message with the next digit 5.
*Mar 2 01:47:06.393: ccCallSetupRequest numbering_type 0x80
*Mar 2 01:47:06.393: ccCallSetupRequest encapType 2 clid_restrict_disable 1
null_orig_clg 0 clid_transparent 0 callingNumber 5000
*Mar 2 01:47:06.393: dest pattern 5, called 55, digit_strip 0
*Mar 2 01:47:06.393: callingNumber=5000, calledNumber=55, redirectNumber=
display_info= calling_oct3a=83
!— The router matches received digits 55 with dial peer 1.
*Mar 2 01:47:06.421: ccCallDisconnect (callID=0x25, cause=0x1 tag=0x0)
*Mar 2 01:47:06.421: ccCallDisconnect (callID=0x24, cause=0x1 tag=0x0)
*Mar 2 01:47:06.425: cc_api_call_disconnect_done(vdbPtr=0x62679168,
callID=0x24, disp=0, tag=0x0)
!— The call was disconnected from the remote router, because
!— the number is incomplete as only 55 is sent, this fails to match any dial
!— peers (dial peers at remote router were four digits in length).
*Mar 2 01:47:06.433: ISDN Se3/0:15: TX -> DISCONNECT pd = 8 callref = 0x801A
*Mar 2 01:47:06.433: Cause i = 0x8081 – Unallocated/unassigned number
!— The call was disconnected because of an unallocated/unassigned number.
Router#

Problems with ISDN Overlap Receiving an Unallocated/Unassigned Number
Understanding debug isdn q931 Disconnect Cause Codes
Using the show isdn status Command for BRI Troubleshooting
Troubleshooting ISDN BRI Layer 3 Using the debug isdn q931 Command
Configuring a T1 or E1 Interface for Outgoing Analog Calls Using the modem dialout controller Command
Configuring and Troubleshooting E1 R2 Signaling for Data Calls
Configuring Dialin and Dialout on the Same T1/E1 PRI Circuits
E1 Error Events Troubleshooting
E1 Layer 1 Troubleshooting Flowchart
T1 PRI Troubleshooting
E1 T1 Troubleshooting

Voice Troubleshooting Tools

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