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yuce_sungur_100's avatar
yuce_sungur_100
Icon for Nimbostratus rankNimbostratus
Apr 13, 2010

tcp half open

The f5 3400 box , we have has BIG-IP 10.0.1 build 283.It seems like when "tcp half open" monitor is set for a pool,F5 is not sending reset packets when it receives "syn-ack" from the pool member.

 

Any idea?misconfiguration or system bug ?

 

management
monitoring
  • hoolio's avatar
    hoolio
    Icon for Cirrostratus rankCirrostratus
    Apr 13, 2010
    Hi ysungur,

     

     

    According to SOL9812, LTM should send a RST after getting the SYN ACK. If you're not seeing this, you could open a case with F5 Support and ask them if the expected behavior has changed in v10.x or if this is a bug.

     

     

     

    https://support.f5.com/kb/en-us/solutions/public/9000/800/sol9812.html

     

     

    Certain BIG-IP monitors use a TCP RST packet to close the monitor connection quickly. For example, the tcp_half_open monitor performs a simple check on the pool member service by sending a TCP SYN packet to the service port. When the monitor receives the SYN-ACK packet from the pool member, the monitor considers the service to be up, and sends a TCP RST packet to the service instead of completing the three-way handshake. The TCP RST packet is typically sent on the server side of the connection, and the source IP address of the reset is the relevant self IP address of the VLAN.

     

     

     

    Aaron