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antesmol's avatar
antesmol
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Jun 11, 2026

F5 https monitor receive string

Hello,

I am testing an HTTPS monitor on BIG-IP 17.1.2.

The server endpoint returns:

HTTP/1.1 200 OK when the service is healthy

HTTP/1.1 503 Service Unavailable when the service is unhealthy

This behavior has been confirmed from the F5 using:

 

curl 

In the HTTPS monitor, I tried the following Receive Strings:

 

-HTTP/1.1 200 

-200 OK

- HTTP 200

but the monitor stays DOWN.

If I use:

 

-ok||200

the monitor goes UP, however it also remains UP when the endpoint returns HTTP 503.

My question is:

How can I configure a standard HTTPS monitor so that it is UP only when the endpoint returns HTTP 200 and DOWN when it returns HTTP 503?

 

Thank you.

3 Replies

  • Give this try for String config on a Monitor.  Other option i can think of is using an iRule

     

    Send String: GET /your-endpoint HTTP/1.1\r\nHost: ://yourdomain.com\r\nConnection: Close\r\n\r\n

    Receive String: HTTP/1.1 200 OK

  • send and receive string config uses regular expression syntax, which "." is also special character

    https://my.f5.com/manage/s/article/K5917