1. IP ADDRESSES Lecture 6: Network Architectures

2. 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..

3. 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, 128.35.0.72

4. Converting to Decimal (Cont.) Peter Smith4  Now, for double the money, what is its equivalent decimal value? 2727 2626 2525 2424 23232 2121 2020 11111111 1286432168421 The binary number 1111 1111 converts into the decimal number: 128 + 64 + 32 + 16 + 8 + 4 + 2 + 1 = 255

5. Figure 4-1 Binary Notation Dotted-decimal notation

6. Example 1 Change the following IP address from binary notation to dotted-decimal notation. 10000001 00001011 00001011 11101111 Solution 129.11.11.239

7. Example 2 Solution Find the error in the following IP Address 111.56.045.78 There are no leading zeroes in Dotted-decimal notation (045)

8. Example 3 (continued) Solution Find the error in the following IP Address 75.45.301.14 In decimal notation each number <= 255 301 is out of the range

9. 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

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

11. 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

12. Figure 4-3 Finding the class in binary notation

13. Figure 4-4 Finding the address class

14. Example 6 Solution Find the class of the following IP addresses 00000001 00001011 00001011 11101111 11000001 00001011 00001011 11101111 00000001 00001011 00001011 11101111 1 st is 0, hence it is Class A 11000001 00001011 00001011 11101111 1 st and 2 nd bits are 1, and 3 rd bit is 0 hence, Class C

15. Figure 4-5 Finding the class in decimal notation

16. Example 7 Solution Find the class of the following addresses 158.223.1.108 227.13.14.88 158.223.1.108 1 st byte = 158 (128<158<191) class B 227.13.14.88 1 st byte = 227 (224<227<239) class D

17. 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.

18. 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.

19. 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

20. 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.

21. 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.

22. 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.

23. Rick Graziani graziani@cabrillo.edu 23 Subnet Example Network address 172.16.0.0 with /16 network mask Using Subnets: subnet mask 255.255.255.0 or /24 172.16.0.0/24172.16.10.0/24 172.16.5.0/24 172.16.25.0/24

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

25. Example 8 Solution Given the network address 132.21.0.0, 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 132.21. The addresses range from 132.21.0.0 to 132.21.255.255.

26. Default Mak  Class A default mask is 255.0.0.0  Class B default mask is 255.255.0.0  Class C Default mask 255.255.255.0

27. 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

28. Example  Example: IP adress  Network address is: 128.143.0.0 (or 128.143)  Host number is: 137.144  Net mask is: 255.255.0.0 128.143137.144

29. Broadcast address Host number is all ones, e.g., 128.143.255.255 Broadcast goes to all hosts on the network Often ignored due to security concerns

30. IPv6 vs. IPv4: Address Comparison  IPv4 has a maximum of 2 32  4 billion addresses  IPv6 has a maximum of 2 128 = (2 32 ) 4  4 billion x 4 billion x 4 billion x 4 billion addresses