IP ADDRESSES Lecture 6: Network Architectures

IP address  address (IP address) is a numerical label assigned to each device (e.g., computer, printer) participating in a computer network that uses the Internet Protocol forcomputer networkInternet Protocol Communication  An IP address is a32-bit address.  The IP addresses are unique..

IPv4 address space  The address space of IPv4 is 232 or 4,294,967,296.  IP addresses consist of four sections  Each section is 8 bits long  Each section can range from 0 to 255  Written, for example,

Converting to Decimal (Cont.) Peter Smith4  Now, for double the money, what is its equivalent decimal value? The binary number converts into the decimal number: = 255

Figure 4-1 Binary Notation Dotted-decimal notation

Example 1 Change the following IP address from binary notation to dotted-decimal notation Solution

Example 2 Solution Find the error in the following IP Address There are no leading zeroes in Dotted-decimal notation (045)

Example 3 (continued) Solution Find the error in the following IP Address In decimal notation each number <= is out of the range

Network prefix and host number  The network prefix identifies a network and the host number identifies a specific host (actually, interface on the network). host numbernetwork prefix

Glassful addressing In classful addressing the address space is divided into 5 classes: A, B, C, D, and E.

Are You the Host or the Network? 11 The 32 bits of the IP address are divided into Network & Host portions, with the octets assigned as a part of one or the other. Network & Host Representation By IP Address Class ClassOctet1Octet2Octet3Octet4 Class ANetworkHost Class BNetwork Host Class CNetwork Host

Figure 4-3 Finding the class in binary notation

Figure 4-4 Finding the address class

Example 6 Solution Find the class of the following IP addresses st is 0, hence it is Class A st and 2 nd bits are 1, and 3 rd bit is 0 hence, Class C

Figure 4-5 Finding the class in decimal notation

Example 7 Solution Find the class of the following addresses st byte = 158 (128<158<191) class B st byte = 227 (224<227<239) class D

Are You the Host or the Network? (Cont.) Peter Smith17  Each Network is assigned a network address & every device or interface (such as a router port) on the network is assigned a host address.  There are only 2 specific rules that govern the value of the address.

Are You the Host or the Network? (Cont.) Peter Smith18  A host address cannot be designated by all zeros or all ones.  These are special addresses that are reserved for special purposes.

Class A Addresses (Cont.) Peter Smith19  There are 16,777,214 Host addresses available in a Class A address.  formula to compute the number of hosts available in any of the class addresses, where “ n ” represents the number of bits in the host portion: (2 n – 2) = Number of available hosts

Class A Addresses (Cont.) Peter Smith20  For a Class A network, there are: 2 24 – 2 or 16,777,214 hosts.  Eg., a Class A address uses 7 bits to designate the network, so (2 7 – 2) = 126 or there can be 126 Class A Networks.

Class B IP Addresses (Cont.) Peter Smith21  So how many Class B Networks can there be?  Using our formula, (2 14 – 2), there can be 16,382 Class B Networks & each Network can have (2 16 – 2) Hosts, or 65,534 Hosts.

Special Addresses (Cont.) Peter Smith22  Within each address class is a set of addresses that are set aside for use in local networks sitting behind a firewall or NAT (Network Address Translation) device or Networks not connected to the Internet.

Rick Graziani 23 Subnet Example Network address with /16 network mask Using Subnets: subnet mask or / / / / /24

Network Addresses The network address defines the network to the rest of the Internet. Given the network address, we can find the class of the address, the block, and the range of the addresses in the block

Example 8 Solution Given the network address , find the class, the block, and the range of the addresses The 1 st byte is between 128 and 191. Hence, Class B The block has a netid of The addresses range from to

Default Mak  Class A default mask is  Class B default mask is  Class C Default mask

masks 27  Subnet masks apply only to Class A, B or C IP addresses.  The subnet mask is like a filter that is applied to a message’s destination IP address. Its objective is to determine if the local network is the destination network. A mask is a 32-bit binary number. The mask is ANDeD with IP address to get The bloc address (Network address) Mask And IP address = Block Address

Example  Example: IP adress  Network address is: (or )  Host number is:  Net mask is:

Broadcast address Host number is all ones, e.g., Broadcast goes to all hosts on the network Often ignored due to security concerns

IPv6 vs. IPv4: Address Comparison  IPv4 has a maximum of 2 32  4 billion addresses  IPv6 has a maximum of = (2 32 ) 4  4 billion x 4 billion x 4 billion x 4 billion addresses