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Core Issue

The show isdn status command has been issued to determine that the issue is related to the physical layer.

This an example of the Layer 1 (L1) status DEACTIVATED:

router#show isdn status 

The current ISDN Switchtype = basic-ni1

ISDN BRI0 interface Layer 1 Status:


If the show isdn status command indicates that the L1 status is DEACTIVATED, then the router is not establishing an L1 connection to the Telco ISDN switch.

Perform these steps, and after each step, issue the show isdn status command to check if L1 is up (ACTIVE):

  1. Issue the shutdown command, followed by the no shutdown command on the BRI interface in question.

    This will ensure that the BRI interface is not administratively down. You can also issue the clear interface bri number command to reset the interface.

  2. Verify that the backup interface command is not configured under the BRI interface. That command deactivates the BRI interface until the backup is initiated. If necessary, issue the no backup interface interface_type interface_number command to remove it.
  3. Issue the show isdn status command to check if the switchtype for the interface is correctly configured. If the switchtype is either not configured or configured incorrectly, configure it on the interface.

This example shows that the switchtype is not configured:   

maui-soho-01#show isdn status

    **** No Global ISDN Switchtype currently defined ****
    ISDN BRI0 interface
    dsl 0, interface
    ISDN Switchtype = none
    Layer 1 Status:
    Layer 2 Status:
    Layer 2 NOT Activated
          Layer 3 Status:
    0 Active Layer 3 Call(s)
    Activated dsl 0 CCBs = 0
    The Free Channel Mask: 0x80000003
    Total Allocated ISDN CCBs = 0

Tip: The Telco should explicitly indicate the switchtype to configure. Occasionally, (especially in North America) the Telco may indicate that the switchtype is custom or national. In such cases, use these guidelines to determine the switchtype configuration:

  • Custom - If the Telco indicates that the switchtype is custom, then configure the switchtype on the router as basic-5ess (for BRI with a 5ess switch), primary-5ess (for PRI with a 5ess switch), basic-dms (for BRI with a DMS switch), or primary-dms (for PRI with a DMS switch).
  • National - A switchtype conforming to the NI-1 standard for BRI and NI-2 standard for PRI. If the Telco informs you that the switchtype is National, then the Cisco router configuration should be basic-ni (for BRI) or primary-ni (for PRI).

Issue the isdn switch-type command to configure the switchtype on the router as shown in this example:

router#configure terminal  
Enter configuration commands, one per line. End with CNTL/Z.
router (config)#isdn switch-type basic-5ess
router (config)#exit
  • Swap the RJ45 cable.
  • Contact your Telco for further circuit testing.
  • Replace the ISDN Wan Interface Card (WIC).

When hardware replacement is indicated after troubleshooting:

  • If you have a hardware support contract directly with Cisco for this part, use the Service Order Submit Tool to request a replacement part directly.
  • For warranty service, please contact the Cisco Technical Assistance Center (TAC) directly at 1-800-553-2447, or online by using the TAC Service Request Tool.
  • If your product is not covered by contract or warranty, contact your Cisco partner or reseller to request a replacement part for the hardware component that is causing the issue.
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