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emile's avatar
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Oct 25, 2023

POST requests lost between two vs intermittently


Since we upgraded our BIG-IP F5 from to, we encountered a loss of POST requests between virtualserver and our backend. This is always the same request which is blocked.

Firstly, we were thinking that the problem was on the backend side because we were able to log  HTTP_REQUEST_RELEASE event everytime. But we decide recently to roolback and the problem disappears.

In order to troubleshoot, we have mounted a temporary virtual server on which we redirect only the specific request.

And then, we were able able to observe that the HTTP_REQUEST_RELEASE occurs every time on the first virtualserver but on the temporary one, we only see CLIENT_ACCEPTED and CLIENTSSL_HELLO. Sometimes the request works and we can see HTTP events on this one.
Any help is appreciated !

4 Replies

  • Hi emile,

    Packet capture can help you troubleshoot the issue.

    Starting from v16.1.0, a new feature available in the HTTP profile. Allow space title name feature, which is disabled by default, may be triggering this issue.

    Allow Space Header Name: Specifies whether to allow white space in an HTTP header between the header name and the separator colon in an HTTP request or response. When Enabled, the BIG-IP system ignores white space between the header name and the colon. This feature is disabled by default.


    • emile's avatar
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      Hi Enes,

      Thanks a lot for your answer. 
      I've tried to pass the value of tmm.http.rfc.allowwsheadername to disable in v14.1.4.6 and I didn't manage to reproduce the issue. 

      To be sure, I'll enable the setting concerned in v17 and see if the problem disappears.


      • emile's avatar
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        Unfortunately, the problem persists with the Allow Space Header Name enabled.