"NFSv4 issues causing denial of service attack on RHEL 6 which reports 'bad sequence-id' error"

Solution Verified - Updated -


  • When RHEL6 clients are connected to our NetApp filer via NFSv4, we see eventually/sporadically see the following errors repeating in /var/log/messages:
Jan 12 09:08:56 xxxx kernel: NFS: v4 server netapp2 returned a bad sequence-id error!
Jan 18 06:04:49 xxxx kernel: NFS: v4 server returned a bad sequence-id error on an unconfirmed sequence ffff880311ebb220!
  • Eventually this results in a DOS attack on both the RHEL 6 servers and the NetApp filer, during this time RHEL 5 servers are oddly unaffected.


  • Red Hat Enterprise Linux 6 (NFS client)
    • kernels prior to kernel-2.6.32-279.22.1.el6
  • NetApp Filer (NFS server)
    • running OnTap 8.02.* or earlier

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