IRule for UDP Traffic

If you create two separate pools and place one member in each, this will work just fine providing you assign the 'main' pool as the default pool for the VS and disable the slow ramp time and priority group activation for each pool;

when CLIENT_DATA {
 if { [active_members main_pool] != 0 } {
  pool main_pool
 }
 else {
  pool backup_pool
 }
}