Specifications

IEEE 802.3 Ethernet Communication
ADDvantage-32 PLUS
8-30
• Class B addresses: (128.x.x.x to 191.x.x.x), subnet mask 255.255.0.0
These addresses use 14 bits for the <network> and 16 bits for the <host> portion of the IP
address. This allows for 214-2 (16382) networks each with 216-2 (65534) hosts; a total of over
1 billion addresses.
• Class C addresses: (192.x.x.x to 223.x.x.x), subnet mask 255.255.255.0
These addresses use 21 bits for the <network> and 8 bits for the <host> portion of the IP
address. That allows for 221-2 (2097150) networks each with 28-2 (254) hosts; a total of over
half a billion addresses.
• Class D addresses: (224.x.x.x to 239.x.x.x)
These addresses are reserved for multicasting (a type of broadcasting, but in a limited area, and
only to hosts using the same class D address).
• Class E addresses: (240.x.x.x to 245.x.x.x)
These addresses are reserved for future use.
8.9.3.2 Broadcast Addressing
An address with all bits one is interpreted as all networks or all hosts. For example,
128.2.255.255 means all hosts on the class B address network 128.2. This is called a directed
broadcast address because it contains both a valid <network address> and a broadcast <host
address>.
8.9.3.3 Multicast Addressing
Multicast devices use Class D IP addresses to communicate. These addresses are contained in
the range encompassing 224.0.0.0 through 239.255.255.255. For each multicast address, there
exists a set of zero or more hosts that listen for packets transmitted to the address. This set of
devices is called a host group. A host that sends packets to a specific group does not need to be
a member of the group. The host may not even know the current members in the group. There
are two types of host groups:
• Permanent: Applications that are part of this type of group have an IP address permanently
assigned by the IANA. Membership in this type of host group is not permanent; a host can join
or leave the group as required. A permanent group continues to exist even if it has no members.
The list of IP addresses assigned to permanent host groups is included in RFC 1700. These
reserved addresses include:
- 224.0.0.0: Reserved base address
- 224.0.0.1: All systems on this subnet
- 224.0.0.2: All routers on this subnet