EMM-E6 Ethernet User's Guide

REVIEW OF ADDRESSING
EMM-E6 User’s Guide 1-23
As MAC addresses are often used to perform management and control
functions for networking hardware, it is important to be able to identify a
MAC address when it is requested or returned by network management.
Since most MAC addresses are set at manufacture and cannot be altered
by users, this manual does not examine MAC addressing in greater detail.
1.10.2 IP Addresses
Each network interface or TCP/IP host is identified by a 32-bit binary
number called the Internetwork Protocol (IP) address. An IP address
represents a connection to the network, but does not identify any specific
physical device location (physical locations are determined by MAC
Addresses, discussed earlier in this chapter). Every IP address is made up
of four 8-bit binary numbers (octets). Each octet is translated into its
decimal equivalent and represented using Dotted Decimal Notation
(DDN). The DDN format is XXX.XXX.XXX.XXX. Any of the four
DDN values, called fields, can range from 1 (octet 0000 0001) to 255
(octet 1111 1111). An IP address is made up of two portions, the Network
ID and a Host ID. Network IDs refer to a particular network and are
assigned by the Internet Assigned Numbers Authority (IANA). The IANA
assigns fixed numbers to one, two, or three of the fields in order to provide
a unique Network ID.
Once a Network ID has been assigned, the Network Manager assigns
individual Host IDs by configuring different values (within the allowable
ranges) for the octets not set by the IANA. This allows individual hosts on
the network to be identified by distinct numerical addresses.
There are three classes of IP addresses which define the Network and
Host ID numbering scheme. Tables 1-1 through 1-3 describe the classes.
The bold type in these tables indicates a field assigned by the IANA, the
Network ID. Any time the term “host” is found in the DDN format
example address, it indicates a Host ID field, which may be assigned by
the network manager.
CH1Book Page 23 Wednesday, March 20, 1996 7:48 AM