Cisco WAN Switching Modules

Field Notice 981012: Co-located NTM and UXM UBU Allocation Problem

October 17, 1998

Revised November 11, 1998

Products Affected




When co-located in a node with NTM Model F while running Cisco IOS release 9.1.03.

Problem Description

Cisco IOS release 9.1.03 highlighted a problem with the mis-allocation of Universal Bus Units (UBU) to an IGX-NTM trunk card in slot 3. When installed in slot 3, the NTM adversely affects messaging between the IGX-NPM (Nodal Processor Module) and the affected IGX-UXM. Affected messages include background diagnostic tests, configuration information and in some instances, user traffic. It is important to note that only the IGX-NTM model F has this problem. Use the dspcd 3 command to verify the IGX-NTM model. Reference the CCO Technical Tip called How to Distinguish Between Different IGX NTM Models for more details.


UBUs, or Universal Bus Units, are the basic unit of allocating bandwidth on the IGX cellbus. As card's ports are activated, sufficient UBUs are allocated to the card to allow the card enough bandwidth to accomodate the traffic. UBUs are typically allocated consecutively.

After a node power outage or node rebuild, UBUs are allocated first to the IGX-NPM and than to the first trunk card. If the IGX-NTM is located in slot 3 of the IGX node, the IGX-NTM is allocated it's UBUs immediately after the NPMs, but before any other card in the node.

Problem Symptoms

The most observable symptoms for the IGX network operator include an indication that the IGX-UXM has failed (use the dspcd slot# or dspcds commands to check to see if the IGX-UXM has failed) or is reporting a missing backcard. Affected users may observe timeouts when accessing remote networked applications or data files. Users may also experience an inability to log into remote servers and resources. In severe instances node unreachability may be reported.

Below is a dspcd screen indicating the symptom.

nodeigx        TN    Service         IGX 8420  9.1.03    Sep. 14 1998 16:35 EST

Missing Cards: 1 T3 <<---

      FrontCard  BackCard                      FrontCard  BackCard 
   Type  Rev  Type     Rev  Status          Type  Rev  Type     Rev  Status
1  NPM   BVN                Standby      9  UXM   AAC  Empty <<---   Active

Another observable symptom are background diagnostics failures which can be observed using the dspcderrs uxm_slot# command.

UXM in Slot 9  : 159890 Rev AAC     Failures Cleared: Sep. 14 1998 16:02:06 EST

----------------------------------- Records Cleared:  Sep. 14 1998 10:03:07 EST
 Self Test          Threshold Counter: 0          Threshold Limit: 300
 Total Pass: 0             Total Fail: 0              Total Abort: 0
 First Pass:                            Last Pass:
 First Fail:                            Last Fail:

 Background Test    Threshold Counter: 0          Threshold Limit: 300
 Total Pass: 50            Total Fail: 3 <<---        Total Abort: 1
 First Pass: Sep. 14 1998 10:06:45 EST  Last Pass: Sep. 14 1998 14:11:46 EST
 First Fail: Sep. 14 1998 14:25:23 EST  Last Fail: Sep. 14 1998 14:32:33 EST

 Hardware Error     Total Events: 0     Threshold Counter: 0
 First Event:                           Last Event:

 This Command: dspcderrs 9


UXM in Slot 9  : 159890 Rev AAC
 Failure Type: UXM Background Test
 Failure Time: Sep. 14 1998 14:32:33 EST

   Last Failure: Timeout - NPM waiting for Data from UXM

   Last Test Data Transmitted (DATA):
 00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F 10 11 12 13

   Last Test Data Received (DATA):
 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  <<---

The above "Last Test Data Transmitted" string of characters should match the "Last Test Data Received" text string exactly to avoid logging a background diagnostic test failure.



There are two workarounds. Method 1 is the easiest of the two, and is preferred.

  1. Physcally move the NTM from slot number 3 to any other slot.

  2. Use the getubus command to allocate additional UBUs to the IGX-NPM controller card. This is a temporary workaround since the getubus was implemented as a debug. Any changes to UBU allocations using this command do not survive a nodal power cycle or a redundant processor switch.


Switch to Cisco IOS release 9.1.04. This software has the fix to correctly allocate UBUs to the IGX-NTMs. If you are a registered CCO user and you have logged in, you can download Cisco IOS release 9.1.04 from Cisco Connection Online.

Bug Details

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

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:

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