iRule

 iRule: --

o iRule is a powerful and flexible feature within the BIG-IP local traffic management (LTM).
o IRule is a powerful & flexible feature That you can use to manage your network traffic.
o It significantly enhances ability to customize content switching to suit your exact needs.
o iRule is a powerful and flexible feature of LTM based on F5's exclusive TMOS architecture.
o iRules are built using TCL-based scripting language allowing arbitrary manipulation of traffic.
o It manipulate traffic flowing through LTM, including real-time modification of defined data.
o iRule is scripting language that we use to take the advantages of extra features of BIG IP.
o Using iRules, it is possible to send traffic specific to individual pool members, Ports & URIs.
o iRules provides more advanced capabilities to LTM in order to meet specific requirements.
o iRules is based upon programming language called the Tool Command Language ( TCL).
o iRules are not enabled until it is applied to the virtual server (VS) in BIG IP System LTM.
o Once iRules is enabled on virtual server, it checks all the traffic passing via a virtual server.
o iRules allows LTM to modify server side & client-side traffic all way up to application layer.
o It is recommended to use an iRule is when you want to add some form of functionality.
o To application & that functionality is not already readily available via built-in configuration.
o iRules are user created Tool Command Language programs that are assigned to VS.
o Run (or triggered) by one or more user specified Events related to that Virtual Server (VS).
o TCL itself is a relatively simple programming language to write, read and understand.
o Tool Command Language (TCL) is the simple but still being very powerful and flexible.
o TCL support Variables, Functions, Operators, external files, encryption, external UDP etc.
o TCL also support TCP connections, Geolocation and security functions more other stuff.
o iRules can be created both in LTM GUI (the Configuration Utility) or at the CLI (using tmsh).
o iRules can be applied to Virtual Server types Standard, forwarding (L 2) & Forwarding (IP).
o iRules can be applied to Virtual Server types Performance (HTTP) & Performance (Layer 4).
o In F5 BIG-IP System LTM, iRules is a script that processes and directs network packets.
o In F5 BIG-IP System LTM, iRules is a script that direct traffic to specific Pool & Pool member.
o An iRule is a TCL script to give more control over how traffic is processed via the LTM.