Dr. John P. Abraham Professor UTPA 21-IP addressing Dr. John P. Abraham Professor UTPA

Addressing Physical –will discuss later Logical

IP address 32 bits Hierarchy – prefix and suffix Prefix identifies the network – given by IANA In classful addressing, the network address (the first address in the block) is the one that is assigned to the organization. The range of addresses can automatically be inferred from the network address. Suffix identifies the computer –given locally No two computers can have the same public IP

Octets IP address is written in 4 octets with separating dots. 10000000.00001011.00000011.00011111 128.11.3.31 One of the UTPA CS address is: 10000001.01110001.10000010.01101110 What is this address in decimal notation?

Classful IP addressing Divided IP address space into three primary classes A, B, C and also there exist class D (multicasting) and E. First four (MSB) bits will determine its class

Size of Network Number Bit field Class Leading Bits Size of Network Number Bit field Size of Rest Bit field Number of Networks Addresses per Network Start address End address Class A     0     8     24     128 (27)     16,777,216 (224) 0.0.0.0 127.255.255.255 Class B    10     16     16,384 (214)     65,536 (216) 128.0.0.0 191.255.255.255 Class C  110     2,097,152 (221)     256 (28) 192.0.0.0 223.255.255.255 Class D (multicast) 1110     not defined 224.0.0.0 239.255.255.255 Class E (reserved) 1111 240.0.0.0 255.255.255.255

Finding the address class

Figure 4.5 Finding the class in decimal notation

Find the class of each address: a. 227.12.14.87 b.193.14.56.22 c.14.23.120.8 d. 252.5.15.111 e.134.11.78.56 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.

LAN The network portion of all IP addresses should be the same on all machines within a LAN You can use VLAN to put machines from different networks together artificially. All computers within a LAN can be made visible to others in the LAN

LAN One should be able to share files with others within the LAN An user of the file should be able to MAP the directory and give a drive letter (in windows) Anyone wanting to connect to machine that does not belong the LAN must go through a routing table (usually located within the Router)

Subnet Addressing 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.

Range of Addresses We often need to find the range of address given to an organization. Find the number of addresses if first and last are given: 146.102.29.0 and 146.102.32.255 There are 256 addresses in the last octet. For the third octet 32. There are 256 addresses in 29, 30, 31 (and 32) for a total of 256*4 = 1024 addresses.

Finding the first and last address given one IP address and the mask To find the first IP address Keep the net portion the same, and turn all host portions to 0. To find the last address: Keep the net portion the same, and turn all host portion to 1s.

Find the first and last IP Given 73.22.17.25 and mask of 255.0.0.0. find the first and last addresses. 73.0.0.0 and 73.255.255.255 How many addresses are in the block? 16,777,216

Finding the network portion Given the IP address and mask, AND Default masks are: For class A 255.0.0.0 For class B 255.255.0.0 For class C 255.255.255.0 However you can create any mask you want based on some rules.

Finding first and last address revisited Find the First address in the block IP address AND network mask Find the last address in the block IP address OR complement of network mask

Example 12 Given the address 23.56.7.91, find the beginning address (network address). Solution The default mask is 255.0.0.0, which means that only the first byte is preserved and the other 3 bytes are set to 0s. The network address is 23.0.0.0.

Example 15 What is the subnetwork address if the destination address is 200.45.34.56 and the subnet mask is 255.255.240.0? Solution We apply the AND operation on the address and the subnet mask. Address ➡ 11001000 00101101 00100010 00111000 Subnet Mask ➡ 11111111 11111111 11110000 00000000 Subnetwork Address ➡ 11001000 00101101 00100000 00000000.

Figure 4.25 Comparison of a default mask and a subnet mask

Table 4.3 Special addresses Private IPs

CIDR notation Classless Inter-Domain routing (CIDR)

CIDR CIDR is an alternative to traditional IP subnetting that organizes IP addresses into subnetworks independent of the value of the addresses themselves. CIDR is also known as supernetting as it effectively allows multiple subnets to be grouped together for network routing. Ddd.ddd.ddd.ddd/m 192.5.48.69/26

CIDR addressing In the address 167.199.170.82/27 the network mask is 255.255.255.224 (27 ones and five zeros). The suffix length of 5, meaning there can be 32 host addresses. We can find the first address by ANDING the IP with mask. We can find the last address by ORing the address with the complement of the mask.

CIDR Prefix length is given after the slash 230.8.24.56/16 gives block of 230.8.0.0 to 230.8.255.255 To find the first address AND the mask. To find the last address, find the complement of the mask, then OR.

CIDR example One of the address in a block is 17.63.110.114/24. Find the number of address, the first address, and the last address of the block. 63 110 114 255 255 0 AND 17 63 110 0 IS THE FIRST ADDRESS --- 63 110 114 0 0 0 255 OR 63 110 255 IS THE LAST ADDRESS

CIDR example 110.23.120.14/20. Find the first and last address 23 120 14 255 240 0 AND 23 112 0 110 23 120 14 0 0 15 255 OR 23 127 255 LAST ADDRESS

Supernetting Class C network addresses are still available, but one may not be enough for an organization. In supernetting we can combine several class C blocks to create a larger range of addresses. If an organization needs 1000 addresses, we can join 4 class C blocks.

Supernet masks For Supernetting we go backwards with the subnet mask. In this case we have 2 less 1s than the default subnet mask. The default subnet mask for class C is 255.255.255.0. In this case we go 2 bits to the left, or 255.255.252.0. In superneting, the number of blocks to combine needs to be a power of 2.