reserved for local network use. There are a possible 2,097,150 Class C
networks of up to 254 hosts each.No host portion of an IP address can be all 0s or 255s. These addresses are
reserved for broadcast addresses. IP addresses with all 0s in the host portion
are reserved for network-to-network broadcast addresses. IP addresses with
all 255s in the host portion are reserved for local network broadcasts.
Broadcast messages are not typically seen by users.
These classes are the standard, but a netmask also determines what class your
network is in. The netmask determines what part of an IP address represents
the network and what part represents the host. Common netmasks for the
different classes are as follows:
Class A—255.0.0.0
Class B—255.255.0.0
Class C—255.255.255.0Because of the allocation of IP addresses for Internet hosts, it is now
impossible to get a Class A network. It is also nearly impossible to get a Class
B network (all the addresses have been given out, but some companies are
said to be willing to sell theirs), and Class C network availability is dropping
rapidly, with the continued growth of Internet use worldwide.
LIMITS OF IPV4 ADDRESSING
The IPv4 address scheme is based on 32-bit numbering and limits the
number of available IP addresses to about 4.1 billion. Many companies and
organizations (particularly in the United States) were assigned very large
blocks of IP addresses in the early stages of the growth of the Internet,
which has left a shortage of “open” addresses. Even with careful allocation
of Internet-connected host IP addresses and the use of network address
translation (NAT) to provide communication to and from machines behind
an Internet-connected computer, the Internet might run out of available
addresses.
To solve this problem, a newer scheme named IP version 6 (IPv6) is being
implemented. It uses a much larger addressing solution that is based on
128-bit addresses, with enough room to include much more information
about a specific host or device, such as Global Positioning Service (GPS)
or serial numbering. Although the specific details about the entire contents
of the an IPv6 address have yet to be finalized, all Internet-related
organizations appear to agree that something must be done to provide more
addresses.