NFS server fails to respond to TCP three-way handshake with SYN_ACK on Red Hat Enterprise Linux 5.9 resulting in a hang on the NFS client

Solution In Progress - Updated -


  • Periodically NFS clients fail to re-establish a previously timed out NFS connection when the three-way handshake fails.

  • NFS client shows symptoms of an unresponsive NFS server in /var/log/messages:

Nov  8 15:18:17 hosta kernel: nfs: server nfsserver not responding, still trying


  • Red Hat Enterprise Linux 5.9
    • kernel 2.6.18-348.6.1.el5
  • NFSv3
  • NFSv4

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