Why does Red Hat Enterprise Linux not respond to SYN requests intermittently?

Solution Verified - Updated -

Issue

  • Why does Red Hat Enterprise Linux intermittently not respond to SYN requests?
  • Server does not answer some specific SYN Packets
  • Webserver does not respond for sessions (SYN requests) sometimes
  • SYN Packets being ignored occasionally by RHEL Apache server
  • LDAP server occasionally dropping SYNs
  • Any server, regardless of the application layer, may occasionally silently drop TCP packets with SYN flag set
  • The Load Balancer which is between client and Red Hat servers is not getting response of SYN packets, the SYN-ACK from the RHEL server goes missing
  • SYN sent through F5 is silently dropped by client
  • What steps need to be taken when clients using TCP Timestamps are hidden behind a NAT?
  • Is it safe to enable net.ipv4.tcp_tw_recycle and/or net.ipv4.tcp_tw_reuse sysctl options in a NAT environment?

Environment

  • Red Hat Enterprise Linux
  • Network traffic using Transmission Control Protocol (TCP)
  • Network with load balancer (such as BigIP F5) or a router which performs Network Address Translation (NAT)

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