The identifier used in the IP layer of the TCP/IP protocol suite to identify each device connected to the Internet is called the Internet address or

Transcription

1 CBCN4103

2 The identifier used in the IP layer of the TCP/IP protocol suite to identify each device connected to the Internet is called the Internet address or IP address. An IP address is a 32-bit address that uniquely and universally defines the connection of a host or a router to the Internet. IP addresses are unique. They are unique in the sense that each address defines one, and only one, connection to the Internet. Two devices on the Internet can never have the same address.

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4 Binary patterns representing IPv4 addresses are expressed as dotted decimals by separating each byte of the binary pattern, called an octet, with a dot. It is called an octet because each decimal number represents one byte or 8 bits.

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7 Change the following IP addresses from binary notation to dotted-decimal notation. a b c d Solution We replace each group of 8 bits with its equivalent decimal number and add dots for separation: a b c d

8 Change the following IP addresses from dotted-decimal notation to binary notation. a b c d Solution We replace each decimal number with its binary equivalent: a b c d

9 Find the error, if any, in the following IP addresses: a b c d Solution a. There are no leading zeroes in dotted-decimal notation (045). b. We may not have more than four numbers in an IP address. c. In dotted-decimal notation, each number is less than or equal to 255; 301 is outside this range. d. A mixture of binary notation and dotted-decimal notation is not allowed.

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12 IP addresses, when started a few decades ago, used the concept of classes. This architecture is called classful addressing. In the mid-1990s, a new architecture, called classless addressing, was introduced and will eventually supersede the original architecture. However, part of the Internet is still using classful addressing, but the migration is very fast.

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19 How can we prove that we have 2,147,483,648 addresses in class A? Solution In class A, only 1 bit defines the class. The remaining 31 bits are available for the address. With 31 bits, we can have 2 31 or 2,147,483,648 addresses.

20 Find the class of each address: a b c d Solution See the procedure in Figure 4.4. a. The first bit is 0. This is a class A address. b. The first 2 bits are 1; the third bit is 0. This is a class C address. c. The first bit is 0; the second bit is 1. This is a class B address. d. The first 4 bits are 1s. This is a class E address..

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22 Find the class of each address: a b c d e Solution a. The first byte is 227 (between 224 and 239); the class is D. b. The first byte is 193 (between 192 and 223); the class is C. c. The first byte is 14 (between 0 and 127); the class is A. d. The first byte is 252 (between 240 and 255); the class is E. e. The first byte is 134 (between 128 and 191); the class is B.

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24 Given the network address , find the class, the block, and the range of the addresses. Solution The class is A because the first byte is between 0 and 127. The block has a netid of 17. The addresses range from to

25 Given the network address , find the class, the block, and the range of the addresses. Solution The class is B because the first byte is between 128 and 191. The block has a netid of The addresses range from to

26 Given the network address , find the class, the block, and the range of the addresses. Solution The class is C because the first byte is between 192 and 223. The block has a netid of The addresses range from to

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28 A mask used to determine what subnet an IP address belongs to. An IP address has two components, the network address and the host address. Subnet Mask IP Address Subnet Address Packet Address Subnet Mask Subnetwork Address

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31 The network address is the beginning address of each block. It can be found by applying the default mask to any of the addresses in the block (including itself). It retains the netid of the block and sets the hostid to zero. Note that we must not apply the default mask of one class to an address belonging to another class.

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34 Given the address , find the beginning address (network address). Solution The default mask is , which means that only the first byte is preserved and the other 3 bytes are set to 0s. The network address is

35 Given the address , find the beginning address (network address). Solution The default mask is , which means that the first 2 bytes are preserved and the other 2 bytes are set to 0s. The network address is

36 Given the address , find the beginning address (network address). Solution The default mask is , which means that the first 3 bytes are preserved and the last byte is set to 0. The network address is

37 Within the address range of each IPv4 network, we have three types of addresses: Network address - The address by which we refer to the network. Broadcast address - A special address used to send data to all hosts in the network. Host addresses - The addresses assigned to the end devices in the network.

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40 No two machines that connect to a public network can have the same IP address because public IP addresses are global and standardized. However, private networks that are not connected to the Internet may use any host addresses, as long as each host within the private network is unique. RFC 1918 sets aside three blocks of IP addresses for private, internal use. Connecting a network using private addresses to the Internet requires translation of the private addresses to public addresses using Network Address Translation (NAT).

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42 Subnetting allows for creating multiple logical networks from a single address block. To create a subnet address, a network administrator borrows bits from the host field and designates them as the subnet field. We create the subnets by using one or more of the host bits as network bits. This is done by extending the mask to borrow some of the bits from the host portion of the address to create additional network bits. The more host bits used, the more subnets that can be defined. For each bit borrowed, we double the number of subnetworks available. For example, if we borrow 1 bit, we can define 2 subnets. If we borrow 2 bits, we can have 4 subnets. However, with each bit we borrow, fewer host addresses are available per subnet.

43 Formula for calculating subnets: 2^n where n = the number of bits borrowed The number of hosts: To calculate the number of hosts per network, we use the formula of 2^n - 2 where n = the number of bits left for hosts.

44 Host bits are reassigned (or borrowed ) as network bits. The starting point is always the leftmost host bit. 3 bits borrowed allows or 6 subnets 5 bits borrowed allows or 30 subnets 12 bits borrowed allows or 4094 subnets

45 To determine the number of bits to be used, the network designer needs to calculate how many hosts the largest subnetwork requires and the number of subnetworks needed. The slash format is a shorter way of representing the subnet mask: /25 represents the 25 one bits in the subnet mask

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49 Provides addressing flexibility for the network administrator. Each LAN must have its own network or subnetwork address. Provides broadcast containment and lowlevel security on the LAN. Provides some security since access to other subnets is only available through the services of a router.

50 IP version 6 (IPv6) has been defined and developed. IPv6 uses 128 bits rather than the 32 bits currently used in IPv4. IPv6 uses hexadecimal numbers to represent the 128 bits.

51 Question -1 We have been given the IP Address and need to "divide" our Classful Class C network into four subnetworks. Maybe into: Marketing Sales Engineering Production Task: What is the Subnet Mask?

52 Question -2 Given the IP Address /29, answer these questions: Notice the /29 on this problem...what's that mean? What is the Class? What is the Default Mask? How many Bits are Borrowed for Subnetting?

53 Question -3 Given the IP Address and we need to create eight usable subnets. Remember: We have only 254 available addresses that we can use. Cannot use.0 Net ID, or.255 Broadcast ID Questions: 1. What is the Default Mask? 2. What is the Subnet Mask? 3. What is the First Subnet ID? 4. How Frequently do Subnet IDs Occurs?