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Roberta_Geranio's avatar
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Apr 22, 2024

curl: (56) SSL read: errno -5961

Hello All, We have an application VIP on F5. User is trying to access the application VIP on F5 using HTTPS from a linux system and the SSL handshake between the application on linux system and the F5 VIP is not working.


we tried using curl to figure where the session is getting droped and we are finding the below error:


  • SSL read: errno -5961
  • Closing connection 0 curl: (56) SSL read: errno -5961

Could you please help me know what could be the possible cause of the issue and anything I can do on the Big-IP side to fix the issue?


The certificate is installed properly on the linux system and the certificate chain is also correct.

The team that manages the F5 part tells us that the network interface it points to on the server side does not have any mismatch on the MTU side which is set to 1500 as well as on the server side. What could be another cause for the problem?


Thanks a lot in advance for your help.



2 Replies

  • You need the certificate and key on the F5 with a clientssl profile attached to the virtual server.  Has that been verified?

  • I think -5961 is the error code for connection reset, which is probably the default action when anything goes wrong in your traffic flow.

    Do you have any iRule code attached to your virtual server?  You see connection reset a lot when an unhandled error happens in an iRule. 

    If it is not too verbose, try looking in the /var/log/ltm file on the device itself.

    For handling a specific error condition gracefully in an iRule, look into the TCL catch statement.