Forum Discussion

Dean_M_21414's avatar
Icon for Nimbostratus rankNimbostratus
Mar 31, 2011

How the F5 monitors IIS6

Hi everyone,



I was getting some really odd behaviour with the F5 http monitor. I couldn't quite explain the symptoms, so I did a full investigation.



If you use an http monitor with a simple GET/\r\n on the F5 to monitor IIS6, please take a read through my findings (file attached to post).







5 Replies

  • Hi Dean,



    That's a very useful document for people new to F5 web app monitoring. If you're interested, you could create an article on Devcentral documenting what you found.



    I have one small suggestion. I'd change your recommendation for 'GET /F5Monitor.aspx\r\n' to 'GET /F5Monitor.aspx HTTP/1.1\r\nHost: \r\nConnection: close\r\n\r\n'. From 10.2.0 on, the monitoring daemon, bigd, no longer appends any \r\n's to the send string for HTTP, HTTPS or TCP monitors. See SOL10655 for details:



    SOL10655: Change in Behavior: CR/LF characters appended to the HTTP monitor Send string




    I've also update the HTTP version to 1.1 and included a blank host header and connection close header. The host header is required for HTTP 1.1. The connection close header tells the server that LTM isn't going to reuse the TCP connection.





  • Dean, this is good stuff. With hoolio's suggestions, I'd also like to encourage you to format this as a tech tip! You can submit articles for review as a member of DevCentral. If you are interested in doing this, there is a video tutorial on configuring windows live writer for submitting articles to DevCentral if you goto Home->Getting Started->DC Misc. The videos are title "Contributing a Tech Tip" and "Configuring WLW for Tech Tips"
  • Hi all,



    hoolio, tks for the advice. I did make the changes to http monitor as you suggested and then tested again. The observed behaviour is the same as previously. I have read the SOL10655 and my doc is now up to date with the reference.



    I've tried adding as a Tech Tip (after watching the appropriate video); however, when I use the word paste function, the images are not pasted. Further I don't have the images available on a URL.



    Jason, hoolio, any chance you guys could possibly post for me? I have attached the updated doc.






  • Sure I can get this converted into a tech tip...probably Monday. Word is the WORST editor. And uploads far too much "extra" formatting. When I used the online editor, I always pasted from Vim or similar. Images are a no go directly, but if you use a blogging tool, it'll upload them for you through the blog api.