REVIEW OF ADDRESSINGEMM-E6 User’s Guide1-23As MAC addresses are often used to perform management and controlfunctions for networking hardware, it is important to be able to identify aMAC address when it is requested or returned by network management.Since most MAC addresses are set at manufacture and cannot be alteredby users, this manual does not examine MAC addressing in greater detail.1.10.2 IP AddressesEach network interface or TCP/IP host is identified by a 32-bit binarynumber called the Internetwork Protocol (IP) address. An IP addressrepresents a connection to the network, but does not identify any specificphysical device location (physical locations are determined by MACAddresses, discussed earlier in this chapter). Every IP address is made upof four 8-bit binary numbers (octets). Each octet is translated into itsdecimal equivalent and represented using Dotted Decimal Notation(DDN). The DDN format is XXX.XXX.XXX.XXX. Any of the fourDDN 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 NetworkID and a Host ID. Network IDs refer to a particular network and areassigned by the Internet Assigned Numbers Authority (IANA). The IANAassigns fixed numbers to one, two, or three of the fields in order to providea unique Network ID.Once a Network ID has been assigned, the Network Manager assignsindividual Host IDs by configuring different values (within the allowableranges) for the octets not set by the IANA. This allows individual hosts onthe network to be identified by distinct numerical addresses.There are three classes of IP addresses which define the Network andHost 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, theNetwork ID. Any time the term “host” is found in the DDN formatexample address, it indicates a Host ID field, which may be assigned bythe network manager.
