irule format/syntax

You are close. the IP::client_addr is a 9.x variable. You want to use the 4.x client_addr. Also, the parantheses around the use pool commands will cause a validation error.

If you go through the 4.x GUI, you can create this rule via the rules wizard. It will look something like this:

 if (client_addr == 161.215.54.193) { 
    use pool MARS-pool1 
 } else { 
    use pool MARS-pool2 
 }

And, yes, there is an online manual available on the 4.x device itself. Look for the "BIG-IP Reference Manual" on the front GUI page. You can also reference the manuals via our tech.f5.com support site (you'll need your support username/password to get in there though). Look for "Chapter 5 - iRules".

-Joe