To manually configure ports to receive the multicast stream, it is important to know how to derive the Layer 2 MAC address for the multicast group 239.1.1.1. The first 4 bits of the 32-bit address are defined as a Class D address (1110); now, only 28 bits of meaningful address space remain. A Layer 2 MAC address has 48 bits. The first 25 bits are static (01005e), leaving only 23 bits for the IP address to be placed. Because there are 28 bits of meaningful IP addresses, 5 bits must be thrown away to allow the remaining 23 bits to fit. As a result of the 5 bits thrown away, 32 multicast IP addresses (2^5) are mapped to a single Layer 2 MAC address.