can iRule work without assigning it to any virtual server ?

Hi SKumar,

in 99,999% of the usecases iRules will be assigned directly to a Virtual Server.

But it's still possible to attach an iRule indirectly to your Virtual Server(s) via certain Profiles (e.g. using iRules within Persistence Profiles) or by using RULE_INIT events with lesser known techniques to interact with them (e.g. Interact with RULE_INIT events via Traffic Policies).

To get an overview which iRule is used you may execute the TMSH command below...

(tmos) show ltm rule

... and check the individual iRule execution counters. Those iRule statistics can also be viewed via LTMs Web UI.

Based on the iRule execution counters and a brief code review of the stuff running in the RULE_INIT event you can finally judge if the iRule is in use or not...

Note: Last but not least, you may try to delete a given iRule. If the iRule is assigned to a configuration object, the deletion would fail with a errmsg displaying where its been currently used.

Cheers, Kai