Syngress - Eleventh Hour Network+ Exam N10-004 Study Guide (11 ...

Multicast, Broadcast, and Unicast 97
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■ Bootstrap protocol (BootP) A communications protocol that allows you
to manage IP addressing usage centrally and to automate the assignment
of logical addresses in an organization’s network.
■ Dynamic host configuration protocol (DHCP) A communications protocol,
based on BootP, that allows you to manage IP addressing usage
centrally and to automate the assignment of logical addresses in an
organization’s network.
DHCP is responsible for handing out a subset of IP addresses that an
administrator configures into what is called a scope.
The scope contains the address space range that has been preconfigured to
be issued to a requesting client.
Uses the concept of a lease, which is an amount of time that a given IP
address will be valid for a computer.
DHCP supports reservations for machines that require a permanent IP
address.
Additional client configuration options are available with DHCP, for example,
domain name service (DNS) address, Windows Internet name service
(WINS) address, and default gateway.
DHCP is a broadcast-based protocol.
DHCP relay agents are used to pass the DHCP broadcast messages across
routers. The configuration is commonly called an IP helper address in Cisco
Systems-based routers. If the router cannot function as a relay agent, each
subnet that has DHCP clients requires a DHCP server.
MULTICAST, BROADCAST, AND UNICAST
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Multicasting can be used to push data to multiple hosts simultaneously.
Characteristics of multicasting are as follows:
■ Designed to handle traffic destined to multiple hosts.
■ Multicast traffic establishes a one-to-many type of transmission, sending
one stream of traffic to each requesting broadcast domain.
■ The IP address that defines a multicast group is a Class D address
(224.0.0.0 to 239.255.255.255).
■ Multicast addresses cannot be used as source addresses for any traffic.
■ A multicast address identifies a group of hosts sharing the same address.
■ Multicast addresses are not assigned to a device, rather, a device proceeds
to listen for and receive traffic destined to a multicast group that it has
joined by some process.
■ Multicasting is UDP-based.
■ A computer uses Internet Group Management Protocol (IGMP) to report
its multicast group memberships to multicast routers.
■ IGMP is required to be used in host computers that wish to participate
in multicasting.