i need irule source client select pool and the redirect pool

Part of the solution below, routing specific clients to dedicated Pools.

I'm not sure I understand your maintenance/out-of-service Pool-routing conditions - do you want just Client A to be routed to Pool2 or Pool3 (when Pool1 is down), or does the same neglecting condition apply to other clients as well? What should happen to Client B when Pool2 is down?

Perhaps it would make the most sense to just route any client (Client A, B, C, and all others) to the Default Pool when a dedicated pool is down? Let me know if you agree, and I can provide an update.

when CLIENT_ACCEPTED {

   Save the name of default pool (as configured in VS Resources Tab) as a variable, before it can be modified by conditional actions below
  set poolDefault [LB::server pool]

  switch [IP::client_addr] {
    "1.1.1.1" {
       Route clients with IP 1.1.1.1 to Pool1
      pool Pool1
    }
    "2.2.2.2" {
       Route clients with IP 2.2.2.2 to Pool2
      pool Pool2
    }
    "3.3.3.3" {
       Route clients with IP 3.3.3.3 to Pool3
      pool Pool3
    }
    default {
       Route to default pool
      pool $poolDefault
    }
  }

}