undefined procedure error in iRule

Hi Darshan, you are right, it´s just adding the pool selection as an additional command i.e. as follows:

    switch [IP::addr [IP::client_addr] mask 255.255.255.0] {
    10.11.1.0   { 
            snat 10.232.11.1
            pool pool_1
        }
    10.11.2.0   { 
            snat 10.232.11.2
            pool pool_2   
        }
    10.11.3.0   { snat 10.232.11.3 }
    default     { snat 10.232.11.8 }
    }

Thanks, Stephan