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f5mkuDefault's avatar
Mar 09, 2021

F5 health-monitor suddenly use tlsv1

Hi experts,


Did anyone encounter such issue using https health monitor where suddenly it communicates with real server using TLSv1 instead of TLSv2?


I have a pair of F5 active-standby. All the while I was using https health monitor and F5 sent query using TLSv1.2. In fact the standby unit is still communicating using TLSv1.2. However the active unit suddenly use TLSv1 which causes the pool member to become inactive.


Hope anyone can advise.


Thank you in advance.

5 Replies

    • hi Lidev, actually we found out it is a bug. Bug ID 739963. The only problem is we need to find out why the sslhandshake failed that trigger this bug.

      F5 has no answer as per the KB




      HTTPS monitors mark a TLS v1.2-configured pool member down and never mark it back up again, even if the pool member is up. The monitor works normally until the SSL handshake fails for any reason. After the handshake fails, the monitor falls back to TLS v1.1, which the pool members reject, and the node remains marked down.


      Once the handshake fails, the monitor remains in fallback mode and sends TLS v1.0 or TLS v1.1 requests to the pool member. The pool member remains marked down.


      This might occur when the following conditions are met:

      -- Using HTTPS monitors.

      -- Pool members are configured to use TLS v1.2 only.


      To restore the state of the member, remove it and add it back to the pool.

      Fix Information



      • Lidev's avatar
        Icon for MVP rankMVP

        The SSL Handshake failed because your Pool members are configured to use TLS v1.2 only.

        Maybe try to add another TLS version like TLS1.1 to see if the bug disappears.