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Miguel_61449's avatar
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Sep 28, 2011

Internal big ip ltm flow consultation

Hello all,



I would like to inquire about the operation of iRules and the http_class in a big-ip ltm system. I have a pretty good idea of how these resources work and can be allocated to virtual servers, however, I have not very clear the order of application of these two resources.



For example, if there is any inconsistency between the definition of iRules and http_class (say, the iRule sends the traffic to pool_A and the http_class send traffic to pool_B and to both resources are associated to the same virtual server) which would be ejecuted? The iRule or the http_class.



Is there any documentation describing in detail the functioning of the internal data flow in a bib-ip f5 and the correlation between iRules and http_class?



Thanks you in advance.




2 Replies

  • Hi Miguel,



    An iRule can have multiple events which execute before and after the HTTP class(es) are evaluated. Here's a quick list:



    CLIENT_ACCEPTED - TCP connection from client to VIP established


    HTTP_REQUEST - client's HTTP request headers parsed


    HTTP_CLASS_SELECTED (if a matching class is found for a request) or HTTP_CLASS_FAILED (if no matching class is found for a request). If a pool is added to the HTTP class and it matches the request, the pool selection will override the VS default pool and any pool selected in the HTTP_REQUEST event.


    LB_SELECTED - pool member selected


    SERVER_CONNECTED - TCP connection from LTM to server established


    HTTP_REQUEST_SEND - just before the HTTP request is sent to the server


    HTTP_REQUEST_RELEASE - last chance to inspect/modify HTTP headers only before request is sent to pool/node (added in v11.0)


    HTTP_RESPONSE - server's HTTP response headers parsed


    HTTP_REQUEST_RELEASE - last chance to inspect/modify HTTP headers only before request is sent to client (added in v11.0)


    SERVER_CLOSED - LTM to server connection closed


    CLIENT_CLOSED - client to VIP connection closed