The "Cell packing interface error" message reports a transient hardware issue with permanent operational impact.

This is a Troubleshooting Article for a PFE ASIC Syslog Event.
To view other documented syslog events related to XMCHIP, XLCHIP, MQCHIP, LUCHIP, EACHIP, and PECHIP, see KB31893 - Master Index of Articles for Troubleshooting PFE ASIC Syslog Events [juniper.net] .

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When a "Cell packing interface error" event occurs, a message similar to the following is reported:

Apr 13 13:41:43.155 router fpc4 XMCHIP(0):XMCHIP(0): FO: Cell packing interface error - data32_err_log 0x11

Indications:

• PFE wedge of the fabric output block and traffic forwarding is permanently compromised

• Alarm will be raised

If this is caused by a transient hardware error, then additional syslog parity events will be reported. If such events are not combined with a parity error syslog message, then the trigger is a software defect not handling properly the packet head going through the lookup and packet tail located at the memory of the XMCHIP center-chip. 

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The following Junos software changes have been performed to avoid such exposure:

• PR1042742 - MPC3E/MPC4E/MPC5E/MPC6E/T4000-FPC5 card may blackhole traffic
• ​JunOS Software has disabled cell-sharing per default to avoid such conditions from 15.1R6-S11, 16.1R7, 17.1R3, 17.2R3, 17.3R2 and 17.4 or higher​
• PR1180397 - MPC cell packing error causing send corrupt packets to fabric with multicast or bridge flood traffic​
• PR1117665 - MPC cell packing interface error and CRC errors are seen with line-rate IPv6 GRE decapsulation feature.

To avoid this exposure disable cell-sharing on MPC2E-NG/MPC3E/MPC4E/MPC5E/MPC6E with the following configuration "set chassis fpc 'slot#' fabric no-cell-share" . A system reboot is needed to activate this configuration.  In Junos OS version 17.4 or higher, cell-sharing is disabled per default on all linecards with XMCHIP

Perform these steps to determine the cause and resolve the problem (if any).  Continue through each step until the problem is resolved.

1. Collect the show command output.

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   Capture the output to a file (in case you have to open a technical support case). To do this, configure each SSH client/terminal emulator to log your session.

   show log messages
show log chassisd
start shell network pfe <fpc#>
show nvram
show syslog messages
exit

2. Analyze the show command output.

   In the 'show log messages', review the events that occurred at or just before the appearance of the "Cell packing interface error" message. Frequently these events help identify the cause.

• No RMA is required

• The generic pfe-disable event script will detect the wedge condition that happens as a result of this event and invoke the pfe-disable action; see   KB31867 - Generic pfe-disable Event Script [juniper.net] . A FPC restart   at a later time is needed to bring the PFE back into service.

• Perform  FPC restart   to recover.

• Contact your technical support representative.

This article is indexed in  KB31893 - Primary Index of Articles for Troubleshooting PFE ASIC Syslog Events [juniper.net] ; tag XMCHIPTSG

2019-10-14: JunOS software changes implemented to avoid this exposure; updated this KB