layout

It looks like you coded the switch statement appropriately, assuming that each hostname with "xxx.xxx" in it matches the incoming hostname fromt he client, and the pool is valid.

If the incoming connections are SSL, though, you'd have to first decrypt those requests via a CLIENT-SSL profile on the BIG-IP, before the iRule would be able to interpret any of the header data, such as the Host.

Are you doing this? If so, you're probably going to get warnings about the domain name on the cert you're using for your CLIENT-SSL profile, as you can only assign a single cert to that profile, and you're trying to use a single SSL vip to host multiple hostnames. That is unless you're using a wildcard cert for usmc.mil.

when HTTP_REQUEST {
  switch [string tolower [HTTP::host] ] {
    sites.xxx.xxx.mil { 
      pool sites.xxx.xxx.mil_pool
    }
    eusmc.xxx.xxx.usmc.mil {
      pool eusmc.xxx.xxx.usmc.mil_pool
    }
    ehqmc.xxx.xxx.usmc.mil {
      pool ehqmc.xxx.xxx.usmc.mil_pool
    }
    tecom.xxx.xxx.usmc.mil {
      pool tecom.xxx.xxx.usmc.mil_pool
    }
    mccdc.xxx.xxx.usmc.mil {
      pool mccdc.xxx.xxx.usmc.mil_pool
    }
    caocl.xxx.xxx.usmc.mil {
      pool caocl.xxx.xxx.usmc.mil_pool
    }
    default {
      pool default_pool
    }
  }
}

Colin