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Syslog message: XMCHIP.*WI.*Input pause buffer exceeded.*Check if the transmitter respects pause frames



Article ID: KB31680 KB Last Updated: 06 Oct 2021Version: 3.0

The "Input pause buffer exceeded" message reports a configuration, permanent impact on packet forwarding, or chip resource 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 - Index of Articles for Troubleshooting PFE ASIC Syslog Events.



When an "Input pause buffer exceeded" event occurs, a message similar to the following is reported:

Nov 13 14:52:51 router0 fpc2 XMCHIP(0): WI1: Input pause buffer exceeded. Check if the transmitter respects pause frames.


  • Flow control mismatch.
  • Traffic impact since ingress buffer overflow.



This is caused by one of the following reasons:

  • Flow control mismatch configuration between the link partners. The flow control is enabled by default on all the non-AE interfaces and disabled by default on the AE interfaces. The flow control configuration should match on both ends at all times. This is true for AE and non-AE interfaces.

  • Lookup chip running out of look up cycles.

  • Permanent impact on packet forwarding



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.

    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

  2. Analyze the show command output.

    In the 'show log messages', review the events that occurred at or just before the appearance of the "Input pause buffer exceeded" message. Frequently, these events help identify the cause.

  • No RMA required.

  • The RE CLI configuration command "set interfaces <IFD> gigether-options no-flow-control" can be used to disable the flow control.

  • Check “show interface <IFD> extensive” to see if there any resource errors. Presence of resource errors indicate permanent impact on packet forwarding or lookup chip running out of look up cycles.

  • Contact your technical support representative if this issue is seen even after disabling the flow control. 

This article is indexed in KB31893 - primary Index of Articles for Troubleshooting PFE ASIC Syslog Events; tag XMCHIPTSG

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.


Modification History:
2019-10-14: Article reviewed for accuracy; no changes required.
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