A.Multicast addresses 224.0.0.0 through 224.0.0.255 are always forwarded because they are transmitted  with Time to Live （TTL） greater than 1.
B.Multicast addresses 224.0.0.5 and 224.0.0.6 are source multicast addresses for OSPF routers.
C.Multicast addresses 224.0.0.13 and 224.0.0.22 are reserved link-local addresses used by PIMv2 and  IGMPv3.
D.Because they would map to overlapping IP multicast MAC addresses， multicast addresses 224.0.1.1  and 238.1.1.1 could not be used together.
E.Multicast address 224.0.1.1 has been reserved for the Network Time Protocol （NTP） by the IANA
F.The administratively scoped multicast addresses 239.0.0.0 through 239.255.255.255 are similar in  purpose to RFC 1918 private unicast addresses.