The "PPE CBO mismatch" message reports a transient hardware issue.

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 "PPE CBO mismatch" event occurs, a message similar to the following is reported:

Nov 21 19:57:55.043 router0 : %PFE-3: fpc2 LUCHIP(1) PPE 9 CBO[21] mismatch, rd 0x042043042045 exp 0x042043042044

Indications:

• No service impact
• It should be a one time error
• Monitor for frequency of errors and contact your technical support representative if seen repeatedly

This is due to a memory integrity check finding an error in the CBO (Conditional Branch Outcome) registers, which are part of the PPE microcode.
The above error appears when the following condition occurs:

• Periodic memory integrity check received an error for CBO
• For corrective action, it is copying the data into shadow memory,
• But shadow memory and actual memory address was found a mismatched memory

Then LUCHIP logs this error and corrects the mismatch. There is no packet drop.

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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.

   {SYSLOGSERVICENOWTOKEN.EN_US}

   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 "PPE CBO mismatch" message. Frequently, these events help identify the cause.

• No action needed

• If seen more than once, collect the debugging information using scripts
  KB31922 - shell script collecting data if packet forwarding at Packet Forwarding Engine is compromised  [juniper.net]

• Restart FPC and monitor for frequency of errors.

• If  the errors are reported for same memory location, shutdown the FPC using power off commands.

  • Run the CLI command request chassis fpc slot # offline ’,
    For more information on the command, see: request chassis fpc ​

• Contact your technical support representative and a RMA may be required

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

Tip: When looking at an event in the logs, it is important to focus on the first error message in a collection of syslog messages. The first error message is usually the cause of all the follow-on error messages. The follow-on collateral damage error messages can be ignored.

2022-10-21: Marking this KB as public, missing from the previous review
2019-10-01: Article reviewed for accuracy; no changes required