IP Addressing INTW 1325

2 What is an IP address? An unique identifier for a computer or device (host) on a TCP/IP network A 32-bit binary number usually represented as 4 decimal numbers separated by a period Example:

3 What is an IP address? Each address is 32 bits wide Valid addresses can range from to WHY? Because b =

4 What is an IP address? Theoretically, a total of  4.3 billion addresses are available WHY? Because 2 32 = 4,294,967,296 10

5 Two addresses in one… Each address consists of two parts 1.The network address 2.The host address Other systems may use more than one address (Ex: IPX)

6 The Five Network Classes 1.Class A – begins with (1 10 ) to ( )* 2.Class B – begins with ( ) to ( ) 3.Class C – begins with ( ) to ( ) * = Addresses beginning with 127 are reserved for loopback ( is YOU)

7 The Five Network Classes 4.Class D – begins with to Reserved for multicasting 5.Class E – begins with to Reserved for future use These should not be used for host addressing

8 Which part belongs to the network and which part belongs to the node? Class A – XXXXXXXX.yyyyyyyy.yyyyyyyy.yyyyyyyy Class B – XXXXXXXX.XXXXXXXX.yyyyyyyy.yyyyyyyy Class C – XXXXXXXX.XXXXXXXX.XXXXXXXX.yyyyyyyy Where X = Network and y = node

9 IP Addresses* Class1 st OctetNetworks IdsHost IDs A = = 16M B = 16K2 16 = 64K C = 2M2 8 = 255 *Numbers not exact

10 There are three IP network addresses reserved for private networks / / /16 These can be used by anyone setting up an internal network. Routers will never forward packets coming from these addresses.

11 Subnetting …can be done for a variety of reasons –Organization –Use of different physical media –Preservation of address space –Security The most common reason is to control network traffic

12 Subnetting In an Ethernet network, all nodes on a segment see all packets transmitted by other nodes on that segment Performance can be adversely affected under heavy traffic loads A router is used to connect IP networks to minimize the amount of traffic each segment must receive

13 Subnet masking Applying a subnet mask allows you to identify the network and node parts of the address. A router will then determine whether the address is local or remote. Network bits are masked as 1s Node bits are masked as 0s Class A – – Class B – – Class C – –

14 Subnet masking

15 Subnet masking Performing a bitwise logical AND between the IP address and the subnet mask results in the network address Ex: Class - B Network Address =

16 A Few Rules… 1.Each device on a node has a unique MAC address 2.Each device on a node needs a unique IP address 3.All devices on the same physical segment share a common network ID (subnet mask) 4.Each physical segment has a unique Network ID (subnet mask)

17 Address Resolution Protocol (ARP) Before an IP packet can be forwarded to another host, the MAC address (usually 6 bytes written in hex (Ex: 02- FE-87-4A-8C-A9) of the receiving machine must be known ARP determines the MAC addresses that correspond to an IP address A router will choose direct paths for the network packets based on the addressing of the IP frame it is handling (different routes to different networks)

18 Direct and Indirect Routing Direct – when nodes are on the same network Indirect – used when the network numbers of the source and destination do not match –Packet must be forwarded by a node that knows hot to reach the destination (a router)