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ifconfig shows dropped rx packets

This document (7007165) is provided subject to the disclaimer at the end of this document.


SUSE Linux Enterprise Server 11 Service Pack 2


ifconfig shows dropped rx packets
After updating to SLES 11 SP2 packets are being dropped
Dropped counter incrementing
rx_dropped counter is incrementing

Customers have reported seeing dropped packets when examining statistics on their network card, bonds, or virtual interfaces. 


Working as designed.


Beginning with kernel 2.6.37, it has been changed the meaning of dropped packet count. Before, dropped packets was most likely due to an error. Now, the rx_dropped counter shows statistics for dropped frames because of:

Softnet backlog full
Bad / Unintended VLAN tags
Unknown / Unregistered protocols
IPv6 frames when the server is not configured for IPv6

If any frames meet those conditions, they are dropped before the protocol stack and the rx_dropped counter is incremented.

Additional Information

Care should be taken to confirm that frames are not being legitimately dropped.  A quick way to test this (WARNING: this test does not work for bonding interfaces) is to start a packet capture:

host:~# tcpdump

And then watching the rx_dropped counter.  If it stops incrementing while the tcpdump is running; then it is more than likely showing drops because of the reasons listed earlier.  If frames continue to be dropped while running tcpdump, investigation should take place to determine root cause.

This effect is seen starting from SLES 11 SP2, as it utilizes a 3.x kernel series. Previous SLES versions do not exhibit it (that are using kernels prior to 2.6.37)

Additional information can be found by researching commit # caf586e5


This Support Knowledgebase provides a valuable tool for NetIQ/Novell/SUSE customers and parties interested in our products and solutions to acquire information, ideas and learn from one another. Materials are provided for informational, personal or non-commercial use within your organization and are presented "AS IS" WITHOUT WARRANTY OF ANY KIND.

  • Document ID:7007165
  • Creation Date:17-MAY-12
  • Modified Date:25-JUL-13
    • SUSESUSE Linux Enterprise Server

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