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Solving ISDN Problems        5


Use Table 5-1 to identify and diagnose common ISDN problems.

  Common ISDN Problems

Problem

Possible Cause

Possible Solution

An ISDN Basic Rate Interface (BRI) or Primary Rate Interface (PRI) connection is slow, or data is corrupted in transit.

Excessive errors on the ISDN line.

Diagnose with the show isdn command. An error count greater than 20 indicates a problem at the telephone company. (See page 5-2 for BRI connections and page 5-5 for PRI connections.)

The PortMaster cannot establish or maintain an ISDN BRI connection.

An incorrect configuration on the port

Use the show isdn command to check the status and configuration of the port (page 5-3).

The PortMaster cannot establish or maintain an ISDN PRI connection.

Use the procedure on page 5-5 to verify the status and configuration of an ISDN PRI port.

Use the procedure on page 5-6 to determine if the PortMaster and the T1 switch are synchronized.

Use the set line0 loopback command to reset the PRI connection at the switch (page 5-8)

The PortMaster cannot establish or maintain an ISDN connection.

Problems with ISDN negotiation or packet exchange.

Use the set debug isdn commands to display ISDN negotiation and packet exchange information to the console (page 5-9).

Troubleshooting an ISDN BRI Connection

If you are having trouble with an ISDN BRI connection, use the following procedures to diagnose the problem.

Verifying LEDs

Verify the LED state:

  1. Check the LED states as follows and compare its behavior to Table 5-2:

    Table 5-2 ISDN BRI LED Indications

    LED Behavior

    Indication

    Solidly lit

    Synchronization and SPID registration

    Flashing slowly

    Synchronization only

    Flashing rapidly

    No synchronization or SPID registration

  2. If the LED indicates no SPID registration, check the SPID and directory number with the show isdn D0 command.

    Verify that the configured SPID and directory number match those given to you by the telephone company, as described in Step 3 on page 5-4.

  3. If the LED indicates no synchronization, check the state of the D channel.
Verify that the D channel is functioning properly by using the show isdn command. The interface state should be F7. If the interface state is not F7, do the following:

Checking the Physical Interface with show isdn

Follow these steps to check the physical interface of ISDN ports:

  1. Enter the show isdn command.
The output displays D channel status for the ISDN BRI ports.
 

Command> show isdn

 

 

 

D

Ports

Bri Layer1

Inits

Uptime

Change

In

Out

Err

----

-----

----------

-----

------

------

---

----

----

D00

(S01/02)

F7-active

1

4days

4days

74974

79221

0

See the PortMaster Command Line Reference for an explanation of this output.

  1. Check the D channel information.
You can display comprehensive information about each BRI port by using the show isdn command and specifying either a logical serial port number associated with the port or a D channel number. For example:
Command> show isdn d0
D00 status -----------------------(127) 88 89 --------- BRI_NI1

Interface state: F7- active
Init count: 1 uptime: 10days last state change: 10days
recv count: 201647 xmit: 217352 errors: 0
numberplan type: Local plan: ISDN E.164

S0 ---------------------------------------------------------------

Ces state: Connected last change: 10days Port state: ESTABLISHED
Directory: 4684400 SPID: 510468440000 regs: 1
Called: Caller: Flags: 0x00
Connects: 1 last connect: 10days b channel: 1 0
Setup: 04 03 08 00 10 18 02 01 01 34 01 4f 70 09 04 01
34 36 38 34 34 30 30 04 02 88 90 18 01 89 34 01

S1 ---------------------------------------------------------------

Ces state: Registered last change: 10days Port state: IDLE

Directory: 4684401 SPID: 510468440101 regs: 1
Called: Caller: 5107352832 Flags: 0x02
Connects: 56 last connect: 0 b channel: 2 1
Setup: 04 03 08 00 10 18 02 01 02 34 01 4f 6c 0c 02 01
35 31 30 37 33 35 32 38 33 32 70 09 04 01 34 36

17210455: msg 5 Disconnect, cause 11 User Busy
17210753: msg 5 Disconnect, cause 1C Invalid Number Format
17268550: msg 5 Disconnect, cause 10 Normal Clearing

  1. Use the following information to diagnose ISDN BRI problems:

For more information about configuring the PortMaster for ISDN, see the PortMaster Configuration Guide.
For more information about configuring the PortMaster for ISDN, see the PortMaster Configuration Guide. For more information about these commands, see the PortMaster Command Line Reference.

Troubleshooting an ISDN PRI Connection

If you are having trouble with an ISDN PRI connection, use the following procedure to diagnose the problem:

  1. Use the show isdn command to display the status of the D channels for ISDN PRI ports.
The output shows
See the PortMaster Command Line Reference for an explanation of this output.
  1. Use the show line0 and show line1 commands to display information about the physical interface.
The following example is from a PortMaster with a PRI EI line:
 

Command> show line0

 

 

----------------------- line0 - E1 Primary Rate ISDN -----------------------

Status: DOWN

F3

Framing: FAS

Encoding: HDB3

PCM: a-law

 

 

 

 

 

 

 

Violations

 

 

 

 

---------------------------------

 

 

Bipolar

1209159

 

 

CRC4

0

 

 

 

E-bit

0

 

 

 

FAS

0

 

High numeric values indicate a possible configuration problem. Changing the framing and encoding with the following commands might solve the problem:
Command> set line0 framing esf|d4|crc4|fas

Command> set line0 encoding b8zs|ami|hdb3

For more information about these commands, see the PortMaster Command Line Reference.

Establishing Synchronization for an ISDN PRI Connection

Use the following procedure to see if the PortMaster and the PRI switch are synchronized:

  1. Set the console and turn on ISDN frame debugging:

    Command> set console
    Setting CONSOLE to admin session

    Command> set debug isdn-d
    Setting ISDN debugging

The following debug output is from a PortMaster 3 with a nonfunctioning ISDN PRI circuit. Physical connectivity might exist between the digital facility demarcation point and the PortMaster 3, but the ISDN PRI D channel is still not operating. The D0: send 00 01 7f pattern originates from the PortMaster 3 and is sent to the switch via the digital facility. The PortMaster 3 normally receives the D0: recv 00 01 73 patterns in response from the switch.
D0: Data Link Down
D0: Data Link Down
D0: send 00 01 7f
D0: send 00 01 7f
D0: send 00 01 7f
D0: send 00 01 7f
D0: Data Link Down
D0: Data Link Down
D0: send 00 01 7f
D0: send 00 01 7f
D0: send 00 01 7f
D0: send 00 01 7f

  1. Check the red and green LEDs on the back of the PortMaster 3.
If the LEDs are solidly lit, the PortMaster is synchronized with the switch and the PRI facility is functioning.
  1. Confirm physical synchronization with the switch by using the show line0 or show line1 command:
 

Command> show line0

 

 

------------------------- line0 - T1 Primary Rate ISDN ---------

Status: UP

Framing: ESF

Encoding: B8ZS

PCM: u-law

Receive Level:

+2dB to -7.5dB

 

Alarms

 

Violations

 

------------------------------------

---------------------------------

Blue

0

Bipolar

102

Yellow

0

CRC Errors

1

Receive Carrier Loss

0

Multiframe Sync

9

Loss of Sync

0

 

If the switch and the PortMaster are synchronized, the line status is up and the amplitude range for the receive level is approximately 9.5 decibels (dB). This command monitors only physical connectivity (PRI facility status).
If your command output shows that the PortMaster 3 PRI facility is synchronized with the switch, they can start the handshaking process to establish the D channel data link for the PRI. The PortMaster does not attempt to establish the D channel until it is physically connected to the switch.

If the PortMaster PRI facility is not connected to and synchronized with the switch, the show line0 command provides no output.

Resetting a PRI Connection at the Switch

If a PRI connection is not functioning, and other troubleshooting measures have not solved the problem, you can reset the PRI connection at the switch by turning loopback mode on and then turning it off 15 seconds later. For example:

Command> set line0 loopback on
Loopback set ON for Line0

Command> set line0 loopback off
Loopback set OFF for Line0

Interpreting Send and Receive Patterns

Check the set debug isdn-d output (see page 5-6). If you never see a recv (receive) pattern, no connectivity exists between the switch and the PortMaster at the D channel level. The telephone service provider needs to investigate the problem.

If you see recv patterns only and no send patterns, a problem exists with the PortMaster 3. Try the following:

Using Debug ISDN Commands

The set debug isdn command sends debug information to the console. These commands toggle on and off. ISDN debugging options are:

 

set debug isdn

Displays ISDN debugging information on the console.

set debug isdn D0

Displays the status of a single BRI.

set debug isdn-d

Displays ISDN frame debugging information on the console.

set debug isdn-d D0

Displays ISDN frame debugging for a single BRI.

set debug termination

Displays detailed port termination information.

set debug off

Clears all debug settings-except ISDN debug settings for a specific D channel-currently active on the PortMaster.

The following is example output from the set debug isdn d0 command:

Command> set debug isdn d0
Enabling isdn tracing d0

isdn_dial; S1 CRN7770
isdn_dodial S1 (0:1) Sending Call Request - 7770
0: Received Call Sent
07 00 01 80
S1 (0:1) DISCONNECT Unassigned Number
S1 (0:1) CALL_CLEAR
S1: Redialing at alternate 56Kbps rate
isdn_dodial S1 (0:1) Sending Call Request - 7770
0: Received Call Sent
07 00 01 80
S1 (0:1) DISCONNECT Unassigned Number
S1 (0:1) CALL_CLEAR

To disable ISDN debugging, issue the command again:

Command> set debug isdn d0
Disabling isdn tracing d0

By using the D0 keyword, you can specify a BRI line to debug:

Command> set debug isdn-d d0

Enabling isdn D tracing d0
D0: send 00 f3 01 03
D0: recv 00 f3 01 03
D0: send 00 f1 01 0f
D0: recv 00 f1 01 0b

 



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