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Forum Discussion

yquirion's avatar
yquirion
Icon for Altostratus rankAltostratus
Mar 05, 2018

iRules and variable initialization

Hello,   I'm new to F5 BigIP and there is something I don't understand well regarding iRules and variables.   I have a VIP on which I have two iRules applied. The first one, the an iRule to log...
application delivery
iRules
LTM
Hannes_Rapp_162's avatar
Hannes_Rapp_162
Icon for Nacreous rankNacreous
Mar 05, 2018

Hello Yanick,

To solve this, you will need to use a different variable name in place of 

script_name
in your second iRule, i.e. 
script_name_intranet
. When writing iRules, in particular if there are other developers involved, it's best to avoid generic variable names like "log", "time" etc. TMM does not want one variable name to be used twice. Although, this will not cause any issues before 2 iRules where a variable name overlaps are applied to the same Virtual Server. While you're at it, check if other iRules have specific-enough variable names to prevent the same issue in future.

Rgds,

  • yquirion's avatar
    yquirion
    Icon for Altostratus rankAltostratus
    Mar 06, 2018

    Hi Hannes,

     

    Thank you very much for the clarification. We were with another brand of load balancer before, using TCL script as well, and we never face that problem with those devices. Maybe they treat each TCL script as one and the variable are flushed after each script execution.

     

    That being said, we will change our approach in developing iRules.

     

    Thanks again and best regards, Yanick