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Msaad's avatar
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Dec 29, 2020

F5 Big IP resets the connection after receiving SynAck



I'm trying to create a pool that includes two members listening on port HTTPS customized port 7000, I'm using https monitor but pool never comes up. they are working only with ICMP. After troubleshooting I found that F5 Big IP is sending tcp resets to the pool members.


PCAP summary:

F5 internal <------SYN---------> pool member

pool member <------SYNACK---------> F5 Internal

F5 internal <------RST---------> pool member


TCP RST Reason Logs:

BIGIP-1 err tmm1[18512]: 01230140:3: RST sent from to, [0x286ee03:2392] No flow found for ACK

BIGIP-1 err tmm[18512]: 01230140:3: RST sent from to, [0x28448cd:263] {peer} handshake timeout

BIGIP-1 err tmm2[18512]: 01230140:3: RST sent from to, [0x28449e5:985] RST from BIG-IP internal Linux host


Any thoughts ?




1 Reply

  • Hello Msaad.


    This could be caused by a bug:


    I would also check that you are not reaching more than 65k connections for that internal IP.

    Just in case, are you using a 'tcp_half_open' monitor?


    Please, share some more info (release, monitor config, etc).