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Rich101's avatar
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Jun 09, 2011

HTTP Monitor - Host Value




I've been scouring the forums for an answer to this but with no luck!


Can anyone detail if it is possible, within a HTTP monitor that's used on a pool to include the IP of the target node as the host value, rather than blank as is the default, for example in the below situation:





Send String:HEAD /index.htm HTTP/1.1\r\nHost: \r\nConnection: Close\r\n





Server1 -


Server2 -



When the F5 issues the send string, is it possible to send the monitor string as:


HEAD /index.htm HTTP/1.1\r\nHost1.1.1.1: \r\nConnection: Close\r\n for Server1


HEAD /index.htm HTTP/1.1\r\nHost: \r\nConnection: Close\r\n for Server2



We've a whole host of servers that will not respond to probes where the Host: value is left blank.


Any suggestions greatly appreciated!






4 Replies

  • i don't think default monitor supports it.



    there is some example of external monitor which should be usable.




    btw, can't u use fqdn instead?
  • You might also try an HTTP 1.0 send string without a host header:



    HEAD /index.htm HTTP/1.0\r\nConnection: Close\r\n\r\n



    For 10.2+ you should use two \r\n's at the end of the send string. For older versions, just one:



    sol10655: Change in Behavior: CR/LF characters appended to the HTTP monitor Send string




    If that doesn't work, you can set a host header with an inbuilt HTTP(S) monitor. However if it needs to be specific to the server being polled, you'd need to create a custom monitor for each pool member. As Nitass said using an FQDN should be a simpler solution.



  • Hi,



    Thanks for both of your replies, unfortunately the servers are only configured to respond to the IP, they do not accept HTTP v1.0 or FQDN host values.


    This is really an issue with none standard config on the servers, but unfortunately it's coming down to us to sort it out, as our previous load balancer automatically used the server IP in the host value.


    We'd considered the option of using an individual monitor for each instance, but we'd need a few hundred of these which would be somewhat of a manual overhead.


    What are the issues with using an external monitor, as I've read that these should only be used when a standard monitor will not do?



    Thanks again.



  • i never used external monitor in production (since i don't need to take care of bigip :p)



    anyway, i understand performance is a topic we concern. keeping eyes on it could be good. there is article by deb. have u seen it before? not sure if it's helpful.



    ltm external monitors: the basics by deb