RHEL6.8: RHEL NFS server periodically does not respond to NFSv3 requests but responds with TCP ACKs to requests

Issue

• Periodically our RHEL6 NFS server stops responding to NFS requests and we see 'nfs: server XYZ not responding, still trying messages in the NFS client's /var/log/messages file
• The unresponsiveness of the NFS server happens for only around 5-10 minutes, then resolves on its own.
• The issue seems to occur around the top of the hour fairly regularly.
• There are 2 clients affected by this issue. The issue seems to only happen on one client at a time.