Cisco IGX 8400 Series Switches

Field Notice: IGX 8430 Clocking Fix For Slot 17 Through 20 Anomaly

January 18, 1999

Products Affected



IGX 8430

The IGX 8430 is also referred to as the IGX 32.

Problem Description

Due to unequal clock bus trace lengths in the IGX 8430 backplane for slots 17, 18, 19 and 20, occasional packet drops are experienced in user data. This problem is observed only when the IGX is using Bus "B". Use the dspbuses command to determine which bus is active in the IGX 8430. The screen below shows that the "A" bus is active while the "B" bus is in standby.

nodename      TN      StrataCom      IGX 8420    9.1.06     Date/Time Not Set

                      Bus Info

Bus Bandwidth usage in Fastpackets/second   (Snapshot)

   Allocated = 92000      ( 8%)
   Available = 1076000    (92%)


Bus A: Active - OK
Bus B: Standby - OK

Last Command: dspbuses

Next Command:

Problem Symptoms

The symptoms are various and include packet drops at the egress end of the connection, card errors, data re-transmits and slow access to remote servers.

It should be noted that there are other causes for these symptoms. These include failing hardware, loose cables, faulty trunks and intermittent connections. If toggling the active bus to bus "A" does not clear the symptoms, this field notice does not apply and other causes for the above symptoms must be investigated.


The IGX 8430 consists of two shelves, an upper shelf and a lower shelf. The two shelves are interconnected via a cable assembly via the backplanes in each shelf. Due to the high clock speeds present in the backplane, the trace lengths for each slot should be relatively the same to prevent race conditions between slots when passing packets of data from card to card. In this instance, the "B" Bus trace lengths were marginal.

This defect is logged in bug ID CSCdk09391. If you are a registered CCO user and you have logged in, you can view bug details.

View CSCdk09391 (registered customers only)



If a problem is noted with traffic transmitting slots 17 through 20, the card and associated connections or trunks may be moved to another slot. To determine whether the observed symptoms are actually caused by the marginal trace lengths, toggle the active bus to bus "A" by using the cnfbus t command; the observed symptoms should cease.


Order part number IGX8430-CONNECTOR= (include the equal sign) to apply to the IGX 8430 lower shelf backplane. Order only one each IGX8430-CONNECTOR= per IGX 8430. This part is available at no cost. The IGX8430-CONNECTOR= may be installed without powering down the node. It is important to note that all IGX 8430 shipped from Cisco since October 15, 1998 do not exhibit this anomaly.

Installation Procedure

Click here to download the installation instructions in PDF file format. Click here for a GIF file showing the insertion tool and connector.

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: