Lecture 4: Designing IP Addressing in the Network I

Planning for Information Network
Lecture 4: Designing IP Addressing in the Network I

Contents:
•Converting IP Addresses Between Decimal and Binary.
•Determining an IP Address Class.
•Private and Public IPv4 Addresses.
•Subnet Mask.

Converting IP Addresses Between Decimal and Binary:
•An IP address is a 32-bit, two-level hierarchical number.
•It is hierarchical because the first portion of the address represents the network, and the second portion of the address represents the node (or host).
•The 32 bits are grouped into four octets, with 8 bits per octet. The value of each octet ranges from 0 to 255 decimal, or 00000000 to 11111111 binary. IP addresses are usually written in dotted decimal notation, which means that each octet is written in decimal notation and dots are placed between the octets.

Converting From Binary to Decimal
0 1 0 0 0 0 0 1
128 64 32 16 8 4 2 1
0 + 64 + 0 + 0 + 0 + 0 + 0 + 1 = 65

Determining an IP Address Class:
•To accommodate large and small networks, the 32-bit IP addresses are segregated into Classes A through E.
•The first few bits of the first octet determine the class of an address; this then determines how many network bits and host bits are in the address.
•Each address class allows for a certain number of network addresses and a certain number of host addresses within a network.
•Using classes to denote which portion of the address represents the network number and which portion represents the node or host address is called classful addressing.