iRule Editor can't find default_pool

You can get the default pool configured on the VIP using LB::server pool. You'll want to do this before the pool has been selected on the TCP connection, so run LB::server in CLIENT_ACCEPTED:

 
 when CLIENT_ACCEPTED { 
  
     Save the name of the default pool 
    set default_pool [LB::server pool] 
 } 
 when HTTP_REQUEST {   
    if { [matchclass [string tolower [HTTP::header User-Agent]] contains $::bots] } {   
       pool p_PUB_botfarm 
    } else {   
       pool $default_pool 
    } 
 } 
 

Denny, I don't think removing the else clause will have the desired result. I don't think a second HTTP request on the existing HTTP connection from a non-bots request would go to the default pool. In general, it's a good practice to explicitly specify a pool for all cases if you do it for any case.

Aaron