Lecture 1 IP V.4 Addressing

1. IP Address Format • IP Address Class • IP Subnet Addressing • Special Addresses Lecture 1 IP V.4 Addressing

2. IP Addressing • Each host on a TCP/IP network is assigned a unique 32-bit logical address that is divided into two main parts : • The network number • The host number • The network number identifies a network and must be assigned by the Internet Network Information Center (InterNIC) if the network is to be part of the Internet.

3. IP Addressing • An Internet service provider (ISP) can obtain blocks of network addressed from the InterNIC and can itself assign address space as necessary. • The host number identifies a host on a network and is assigned by the local network administrators.

4. IP Address Format • The 32-bit IP address is grouped 8 bits at a time, separated by dots and represented in decimal format (known as dotted decimal notation).

5. IP Address Format 32 bits Network ID Host ID 8 bits 8 bits 8 bits 8 bits Dotted Decimal notation 172 122 16 204 An IP Address Consists of 32 Bits, Grouped into 4 Octets

6. IP Address Class • IP addressing supports five different address classed: A, B, C, D and E. • Only classes A, B and C are available for commercial use. The left-most ( high-order ) bits indicate the network class.

7. IP Address Class Number of Bits Network/ Host 7/24 14/16 21/8 Not for commercial use - Address Range 1.0.0.0 to 126.0.0.0 128.1.0.0 to 191.254.0.0 192.0.1.0 to 223.255.254.0 224.0.0.0 to 239.255.255.255 240.0.0 to 254.255.255.255 High – Order Bit (s) 0 1,0 1,1,0 1,1,1,0 1,1,1,1 Max. Hosts 16,777,214 (224-2) 65,534 (216-2) 254 (28-2) - - IP Address Class A B C D E Format N.H.H.H N.N.H.H N.N.N.H - - Purpose Few large Organizations Medium - size Organizations Relatively Small Organizations Multicast Groups (RFC 1112) Experimental

8. IP Address Class 8 21 14 16 24 Bits 7 Class A 0 Network Host Host Host 64 32 16 8 4 2 1 Class B 1 0 Network Network Host Host Class C 1 1 0 Network Network Network Host A Range of Possible Values Exists for the First Octet of Each Address Class

10. IP Address Class • The class of address can be determined easily by examining the first octet of the address and mapping that value to a class range in the following table.

11. IP Address Class Address class First octet In decimal High – order bits Class A Class B Class C Class D Class E 1 – 126 128 – 191 192 – 223 224 – 239 240 - 254 0 10 110 1110 1111 A Range of Possible Values Exists for the First Octet of Each Address Class

12. IP Subnet Addressing • IP networks can be divided into smaller called “subnetworks or subnets ” • Subnetting provides the network administrator with several benefits, including extra flexibility, more efficient use of network addressed, and the capability to contain broadcast traffic (a broadcast will not cross a router).

13. broadcast traffic • Broadcast traffic is traffic that is simultaneously addressed to all computers connected to the network • Ss opposed to unicast or multicast traffic • For example in the network 192.168.0.0/24 (192.168.0.xxx with subnet mask 255.255.255.0) the broadcast address is 192.168.0.255 • In MAC addressing (layer 2 on the OSI model), the broadcast address is the MAC address FF:FF:FF:FF:FF:FF

14. Example : YRU Network

15. YRU SubnetworkConcept

16. IP Subnet Mask • A subnet address is created by borrowing bits from the host field and designing them as the Subnet field. • The number of borrowed bits varies and is specified by the subnet mask. • Subnet masks use the same format and representation technique as IP addresses. The subnet mask, however, has binary 0s in all bits specifying the Host field.

17. IP Subnet Mask 1 2

18. IP Subnet Mask

19. IP Subnet Mask 3

20. IP Subnet Mask

21. IP Subnet Mask Example subnet mask for Class B address Class B Address : before subneting 1 0 Host Host 1 0 Subnet Host Class B Address : after subneting Bits Are Borrowed from the Host Address Field to Create the Subnet Address Field

22. IP Subnet Mask Example subnet mask for Class B address Network Network Subnet Host Binary representation 11111111 11111111 11111111 00000000 Dotted decimal representation 255 255 255 0 Subnet Mask bits should come from the high-order (left-most) bits of the host field. Default of Class B and C subnet mask types follow. A Sample Subnet Mask Consists of All Binary 1s and 0s

23. IP Subnet Mask 8 4 2 1 32 128 16 64 0 0 0 0 128 0 1 = 0 0 0 0 0 0 192 0 1 = 0 1 224 0 0 0 0 1 1 = 0 1 0 0 0 0 240 1 1 = 1 1 1 0 0 0 1 1 = 1 1 248 1 1 0 0 1 1 = 252 1 1 1 1 1 0 254 1 1 = 1 1 1 1 1 1 255 1 1 = 1 1 Subnet Mask Bits Come From the High-Order Bits of the Host Field

24. IP Subnet Mask Number of Bits 2 3 4 5 6 7 8 9 10 11 12 13 14 Subnet Mask 255.255.192.0 255.255.224.0 255.255.240.0 255.255.248.0 255.255.252.0 255.255.254.0 255.255.255.0 255.255.255.128 255.255.255.192 255.255.255.224 255.255.255.240 255.255.255.248 255.255.255.252 Number of Subnets 4 8 16 32 64 128 256 512 1024 2048 4096 8192 16,384 Number of Hosts 16,382 8190 4094 2046 1022 510 254 126 62 30 14 6 2 Class B Subnetting Reference Chart

25. IP Subnet Mask • The default subnet mask for a Class B address that has no subnetting is 255.255.0.0, while the subnet mask for Class B address 158.108.0.0 that specifies 8 bits of subnetting is 255.255.255.0. • The reason for this is that 8 bits of subnetting, or 28 • (1 for the network address and 1 for the broadcast address) = 256 subnets possible, with 28-2 = 254 hosts per subnet.

26. IP Subnet Mask Class B address 158.108.0.0 Subnetting Reference Chart

27. IP Subnet Mask Number of Bits 2 3 4 5 6 Number of Subnets 4 8 16 32 64 Number of Hosts 62 30 14 6 2 Subnet Mask 255.255.255.192 255.255.255.224 255.255.255.240 255.255.255.248 255.255.255.252 Class C Subnetting Reference Chart

28. IP Subnet Mask Class C Subnetting Reference Chart

29. IP Subnet Mask • The subnet mask for a Class C address 192.168.2.0 that specifies 5 bits of subnetting is 255.255.255.248 With 5 bits available for subnetting, 25-2 = 32 subnets possible, with 23-2 = 6 hosts per subnet.

30. How Subnet Masks Are Used to Determine the Network Number • The router performs a set process to determine the network (or, more specially, the subnetwork) address. • First, the router extracts the IP destination address from the incoming packet and retrieves the internal subnet mask. It then performs a logical AND operation to obtain the network number.

31. How Subnet Masks Are Used to Determine the Network Number • This causes the host portion of the IP destination address to be removed, while the destination network number remains. • The router then looks up the destination network number and matches it with an outgoing interface. • It forwards the frame to the destination IP address. Specifics regarding the logical AND operation are discussed in the following section.

32. Logical AND Operation Output Input Output 1 0 0 0 Input 1 0 1 0 Input 1 1 0 0

33. Logical AND Operation Network Subnet Subnet Destination IP address 00000001 11111111 00000010 00000000 171.16.1.2 Subnet Mask 255.255.255.0 00000001 00000000 Subnetwork Number 171.16.1.0 Applying a Logical AND to the Destination IP Address – the Subnet Mask Produces the Subnetwork Number

35. Example of Network addresses

36. Example of direct broadcast address

37. Example of limited broadcast address

38. This host on This address

39. Example of specific host on this network

40. Example of loopback address