Networking and Distributed Computing

Transcription

1 Networking and Distributed Computing Lecture2: IP Address Classes Assistant lecturer: Suad Alasadi 14/3/2016

2 Subnet Mask Using Subnet Mask to determine the Network address, Broadcast Address, First IP Address, Last IP Address, from host : / Host IP Add Subnet Mask Anding Network Address 2

3 Addressing Subnet Mask Broadcast Address Network Address Wild Cast Address Broadcast Address Note : Wild Cast Address complement of Subnet Mask Network Address = First IP Address = Range of IP Addresses = To Broadcast Address =

4 Private and Public IPv4 Addresses IP address space is divided into public and private spaces. Private addresses are reserved IP addresses that are to be used only internally within a company s network, not on the Internet. public addresses designated for use in networks that are accessible on the Internet

5 Private and Public IPv4 Addresses The following figure illustrates the use of private and public addresses in a network.

6 Private and Public IPv4 Addresses RFC 1918, Address Allocation for Private Internets, defines the private IP addresses as follows: to to to The remaining addresses are public addresses.

7 Interconnecting Private and Public Addresses *The network use private and public address * A router or firewall act as the interface between the private and public IP address. * Network Address Translation (NAT) or *Port Address Translation (PAT) *used to translate from private to public addresses and vice versa. *NAT or PAT is required if accessibility to the public Internet or public visibility is required. 7

8 Interconnecting Private and Public Addresses Example of NAT 8

9 IP Address Classes IPv4 addresses are categorized into five classes: A, B, C, D, and E. Only Class A, B, and C addresses are used for addressing devices. Class D is used for multicast groups. Class E is reserved for experimental use. This use of address space is referred to as classful addressing. 9

10 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.

11 Determining an IP Address Class Determining an IP Address Class from the First Few Bits of an Address.

12 IP Address Classes Class Format Higher Order Bits Address Range No. of Network No. of hosts per Net. A N.H.H.H to ,777,214 B N.N.H.H to C N.N.N.H to ,097, Class D addresses have higher-order bits 1110 and are in the range of to Class E addresses have higher-order bits 1111 and are in the range of to

13 Determining an IP Address Class The following table shows the address format, the address range, the number of networks, and the number of hosts for each of the classes. NOTE The address (any address starting with decimal 127) is reserved for loopback is also reserved and cannot be used to address devices.

14 Class A Blocks The class A address block was designed to support extremely large networks with more than 16 million host addresses. Class A IPv4 addresses used a fixed /8 prefix with the first octet to indicate the network address. The remaining three octets were used for host addresses. To reserve address space for the remaining address classes, all class A addresses required that the most significant bit of the high-order octet be a 0. This meant that there were only 128 possible class A networks, /8 to /8, before taking out the reserved address blocks. Even though the class A addresses reserved one-half of the address space, because of their limit of 128 networks, they could only be allocated to approximately 120 companies or organizations.

15 Class B Blocks Class B address space was designed to support the needs of moderate- to large-size networks with more than 65,000 hosts. A class B IP address used the two high-order octets to indicate the network address. The other two octets specified host addresses. As with class A, address space for the remaining address classes needed to be reserved. For class B addresses, the most significant 2 bits of the highorder octet were 10. This restricted the address block for class B to /16 to /16. Class B had slightly more efficient allocation of addresses than class A because it equally divided 25 percent of the total IPv4 address space among approximately 16,000 networks.

16 Class C Blocks The class C address space was the most commonly available of the historic address classes. This address space was intended to provide addresses for small networks with a maximum of 254 hosts. Class C address blocks used a /24 prefix. This meant that a class C network used only the last octet as host addresses, with the three high-order octets used to indicate the network address. Class C address blocks set aside address space for class D (multicast) and class E (experimental) by using a fixed value of 110 for the three most significant bits of the high-order octet. This restricted the address block for class C to /16 to /16.

17 Class C Blocks Although it occupied only 12.5 percent of the total IPv4 address space, it could provide addresses to 2 million networks.

18 IP Classes

19 Thank You