multicast, and broadcast. Each type of address is used according to the
purpose of the information being sent, as explained here:
Unicast—Sends information to one specific host. Unicast addresses are
used for Telnet, FTP, SSH, or any other information that needs to be
shared in a one-to-one exchange of information. Although it is possible
that any host on the subnet/network can see the information being
passed, only one host is the intended recipient and will take action on the
information being received.
Multicasting—Broadcasts information to groups of computers sharing
an application, such as a video conferencing client or an online gaming
application. All the machines participating in the conference or game
require the same information at precisely the same time to be effective.
Broadcasting—Transmits information to all the hosts on a network or
subnet. Dynamic Host Configuration Protocol (DHCP) uses broadcast
messages when the DHCP client looks for a DHCP server to get its
network settings, and Reverse Address Resolution Protocol (RARP) uses
broadcast messages for hardware address-to-IP address resolution.
Broadcast messages use .255 in all the host octets of the network IP
address. (10.2.255.255 broadcasts to every host in your Class B
network.)Hardware Devices for Networking
As stated at the beginning of this chapter, networking is one of the strong
points of the Linux operating system. This section covers the classes of
devices used for basic networking. Note that this section talks about hardware
devices, and not Linux networking devices, which are discussed in the section
“Using Network Configuration Tools.”
Network Interface Cards
A computer must have a network interface card (NIC) to connect to a
network. Currently, there are several topologies (ways of connecting
computers) for network connections. These topologies range from the old and
mostly outdated 10BASE-2 to the much newer and popular wireless Wi-Fi, or
802.11 networking.
Each NIC has a unique address (the hardware address, known as Media
Access Control [MAC] address), which identifies that NIC. This address is six
pairs of hexadecimal bits separated by colons (:). A MAC address looks