Cisco Signaling Controllers

Field Notice: SC2200 ISDN Timers Will Stop Working

September 25, 2001

Products Affected



SC2200 Release 7.x(x)

All systems running release 7 of the SC2200 will be affected.

Problem Description

The ISDN timers in the SC2200 Signaling Controller (SC) will stop working on each day and time shown below. Time is Eastern Standard Time (EST).

  • Sep 17 2001 07:49:41

  • Nov 5 2001 23:52:27

  • Dec 25 2001 16:55:14

  • Feb 13 2002 09:58:01

  • Apr 4 2002 03:00:48

  • May 23 2002 03:00:49 (Daylight Savings Time added 1 hour here.)

The loss of ISDN timers will cause a loss of the monitoring capability of the Redundant Link Manager and the ISDN Layer 2 stack. If an access server connected to the SC2200 goes out of service after the system passes one of these times, the SC2200 will not know the unit is out of service and will continue to route calls to the access server. Channel Signaling System 7 (SS7) calls will fail with Release Cause of Recovery on Timer Expiry.


caution Caution:?Do not use this procedure in a live system. A service outage will occur.

Listed below are steps an administrator can take to confirm this problem in the system. This procedure is listed for information only.

  1. Stop the SC software.

  2. Change Unix time to 15 minutes before one of the times listed in the section "Problem Description".

  3. Restart the SC software.

  4. Reload one of the network access servers connected to the SC2200.

    The tester should see alarms and corresponding cics would be gateway blocked. In this case, the SC recognizes the network access server (NAS) as Out of Service.

  5. Wait until the time is later than the chosen test time.

  6. Reload a NAS.

    There should not be alarms indicating the NAS went down. The associated cics would still be listed as in service in the SC2200. In this case, the SC2200 does not recognize the NAS as Out of Service.

  7. Perform failover and failback on the SC2200, and then retest.

  8. Set the SC2200 to the correct time.

Problem Symptoms

  • NAS and SC states are mismatched.

    • SC2200 commands rtrv-sc and rtrv-dest will show components In Service.

    • AS5xx0 command show isdn status will show the Layer 2 with a State of Awaiting Establishment.

    • AS5xx0 command debug isdn q921 will show the AS5xx0 continually transmitting (TX) SABME messages but not receiving (RX) a SC2200 response.

  • Excessive SS7 call failures with Release Cause of Recovery on Timer Expiry.

  • In the platform.log, an excessive number of ?Error allocating packet? messages. An example message is ?Error allocating packet (5) for channel 140001?.


The workaround is to perform a failover and failback on the SC2200. This should temporarily clear the issue until the system passes through another of the times listed in the section "Problem Description".

The solution for this issue is contained in release 7.4(11) patch 58 or later. This patch should be applied to all systems running release 7.4(11) as soon as the patch is made available on CCO. Patch 58 should be available on CCO during the first week of October.

If live sites have not been able to apply the patch by November 5, 2001 23:52:27 EST, the system adminstrator should plan a failover and failback of the SC2200 during the night following that time transition. This will clear the issue until the December occurrence listed in the problem description.

For information about resolutions in other releases of the SC2200, please contact the Cisco support team.


To follow the bug ID link below and see detailed bug information, you must be a registered user and you must be logged in.




"PRIIP Q.921 link drops and does not recover" This is the primary DDTS used to track this issue

For More Information

If you require further assistance, or if you have any further questions regarding this field notice, please contact the Cisco Systems Technical Assistance Center (TAC) by one of the following methods:

Receive Email Notification For New Field Notices

Product Alert Tool - Set up a profile to receive email updates about reliability, safety, network security, and end-of-sale issues for the Cisco products you specify.