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nikhilmbass's avatar
nikhilmbass
Icon for Altocumulus rankAltocumulus
Dec 01, 2022

Help in Send/Receive string for F5 Health Monitor

Hello All,

Can someone help me understand what parameters would be checked and response received with the backend pool member, for the below health monitor configured for one of our setups.

Send String : GET / HTTP/1.1\r\nHost: \r\nConnection: Close

Empty field in Received

application delivery
  • Amine_Kadimi's avatar
    Amine_Kadimi
    Icon for MVP rankMVP
    Dec 01, 2022

    Hi,

    Your send string means that you are requesting the root of your http server (or /), and that you are willing to talk to it with the specified http version (1.1). And because the host header is mandatory when using http 1.1, you must send a host header. While this example is sending an empty header (just to comply with the http 1.1 rfc), you may sometimes specify the correct hostname of your application to be sure you are getting the correct answer from the server. Monitors don't need to keep the connection alive, so you also tell the server to close it immediately. 

    Regarding the receive string, because it is empty, any response from the http server will be considered as a valid answer and the member marked up. You may want to parse the response and make sure an exact string exists within it before marking the server up, for this you specify the string to match in that field. 

    Examples for receive string can be any text within the html (e.g. Welcome to my awesome server) or within the status or the headers (e.g. 200 OK)