Today we will discuss

1
Today we will discuss

• IP Addressing
• Subnetting
• This is probably the most important topic
• for the exam. Try to memorize the tables
• and numbers where indicated since they will
• help immensely on the exam.

2
IP Addressing Fundamentals

• If a device wants to communicate using TCP/IP, it
  needs an IP address.
• Any device that can send and receive IP packets
  is called an IP host.
• IP addresses consist of a 32-bit number, usually
  written in dotted-decimal notation.

3
IP Address Fundamentals (cont.)

• Each byte (8 bits) of the 32-bit IP address is
  converted to its decimal equivalent (hence,
  decimal of dotted-decimal notation).
• Each of the decimal numbers in an IP address is
  called an octet.
• The term octet is just a vendor-neutral term
  instead of byte.

4
IP Address Fundamentals (cont.)

• For example 168.1.4.25
• The first octet is 168.
• The second octet is 1.
• The third octet is 4.
• The fourth octet is 25.
• The RANGE of decimal numbers in each octet is
  between 0 and 255, inclusive. (256 numbers total)

5
Other IP Terminology

• Bit a bit is one digit either a 1 or a 0.
• Byte a byte is 8 bits.
• Network address also called the network number,
  uniquely identifies each network. Every machine
  on the same network shares that network address
  as part of its IP address.
• Host address also referred to as a node
  address, is assigned to and uniquely identifies
  each machine on a network.
• Broadcast address - sent to all nodes on the
  network

6
Binary to Decimal

• Conversion

7
Binary

• The ability to convert from binary to decimal and
  back again is very handy when working with IP
  addresses.
• The digits used are limited to either a 1 (one)
  or a 0 (zero).
• Only convert up to 8 bits at a time (an octet).

8
Binary (cont.)

• The trick to binary is to learn the decimal
  values of each bit for the first 8 bits.
• Start from the left or right and add.
• Just add the decimal values where there is a 1
  (one) present, and you will have the decimal
  value of the octet.
• The next slide shows the decimal value of each
  bit value.

9
Binary to Decimal for 204

• Binary 1100 1100 Decimal 204
• 64 32 16 8 4 2
  1
• 1 1 0 0 1 1
  0 0
• --------------------------------------------------
  ---------
• 64 0 0 8 4 0 0
• 
  
• 
  204

10
Memorize

• Binary 1111 1111 Decimal 255
• Binary 0000 0000 Decimal 0
• Know the values 128-64-32-16-8-4-2-1.
• The easiest way to remember it is to start at 1
  and multiply by 2.
• 1 2 2 2 4 2 8 2 16 2 32 2
  64 2 128.

11
Decimal to Binary

• Convert 212 to binary.
• Do the math.
• Answer 11010100

12
Another Binary to Decimal Memorization Chart
(see why this is important in a few slides)
13
Hierarchical IP Addressing Scheme

• An IP address consists of 32 bits of information.
• The address is broken into four 8-bit (1
  byte) groups, converting each octet to decimal
  values, and separating these values by dots
  (dotted decimal notation).
• Example 172.16.30.56

14
Hierarchical IP Addressing (cont.)

• Two other ways to represent dotted- decimal
  172.16.30.56 are
• Binary
• 10101100.00010000.00011110.00111000
• Hexadecimal
• AC.10.1E.38
• See end of presentation for hex conversion notes
  and chart.

15
The Classes of Networks
16
Classes of Networks

• All addresses in the same class A, B, or C
  network have the same numeric value NETWORK
  portion of the address. The rest of the address
  is called the HOST portion of the address.
• When written down, network numbers have all
  decimal 0s in the host part of the number.

17
Classes of Networks (cont.)

• Network number example
• Class A byte. 0. 0. 0
• Class B byte. byte. 0. 0
• Class C byte. byte. byte. 0
• However, network numbers are not actually IP
  addresses because they cannot be assigned to an
  interface as an IP address.

18
List of All Possible Valid Network Numbers
(memorize)
19
Details of Classes A, B, C

• Before starting to design subnets, you should
  know what it is that you've been given. Here are
  three ways of finding out what class your
  allocation is in. Use whichever you find easiest.
  
• Class A addresses begin with 0xxx binary, or 1 to
  126 decimal. (127 is loopback)
• Class B addresses begin with 10xx binary, or 128
  to 191 decimal.
• Class C addresses begin with 110x binary, or 192
  to 223 decimal.
• If the first bit is 0 it is a Class A address
• If the first two bits are 10 it is a Class B
  address
• If the first three bits are 110 it is a Class C
  address

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Reserved IP Addresses

• Address of all 0s
• Address of all 1s
• Network 127.0.0.1

• Means network address or this network segment
• Means broadcast
• Reserved for loopback tests. Allows local node to
  send a test packet to itself without generating
  network traffic.

21
Private IP Addresses

• These addresses can be used on a private network,
  but are not routable on the Internet.
• With these addresses, use Network Address
  Translation (NAT) to access the Internet via a
  legal IP address.

22
SUBNETTING

• .

23
Memorize Powers of 2

• 21 2
• 22 4
• 23 8
• 24 16

• 25 32
• 26 64
• 27 128
• 28 256

24
Subnet Masks

• A subnet mask is a 32-bit binary number usually
  written in dotted-decimal format.
• The 1s in the subnet mask represent the network
  (or subnet) part of the IP address.
• The 0s represent the host part.
• Example
• Binary 11111111.11111111.11111100.00000000
• Dotted-decimal 255.255.252.0 (same number)

25
Subnet Masks (cont.)

• Slash notation (/) at the end of an IP address
  means how many bits are turned on (1s).
• Ex 192.168.10.32 /28
• Where /28 is subnet mask 255.255.255.240

26
Default Subnet Mask

• Not all networks need subnets, meaning they use
  the default subnet mask.

27
Five questions to answer when calculating

• How many subnets does the chosen subnet mask
  produce?
• How many valid hosts per subnet are available?
• What are the valid subnets?
• Whats the broadcast address of each subnet?
• What are the valid hosts in each subnet?

28
Easier than it looks

• How many subnets?
• 2x 2 number of subnets.
• x is the number of masked bits, or the 1s. For
  example, in 11000000, the number of ones gives us
  22 2 subnets. In this example, there are 2
  subnets.

29
Easy (cont.)

• 2) How many hosts per subnet?
• 2y 2 number of hosts per subnet.
• y is the number of unmasked bits, or the 0s. For
  example, in 11000000, the number of zeros gives
  us 26 2 hosts. In this example, there are 62
  hosts per subnet.

30
Easy

• 3) What are the valid subnets?
• 256 subnet mask block size, or base number.
  For example, for subnet mask 255.255.192.0, 256
  192 64. 64 is the first subnet. The next subnet
  would be the base number plus itself, or 64 64
  128, (the second subnet). You keep adding the
  base number to itself until you reach the value
  of the subnet mask, which is not a valid subnet
  because all subnet bits would be turned on (1s).

31
Easy

• 4) Whats the broadcast address for each subnet?
• The broadcast address is all host bits turned
  on, which is the number immediately preceding the
  next subnet (example in a minute).
• 5) What are the valid hosts?
• Valid hosts are the numbers between the subnets,
  minus the network (subnet) numbers and broadcast
  numbers.

32
Calculating Class C, Example 1

• Network address 192.168.10.0
• Subnet mask 255.255.255.192
• Just answer the five questions
• 1) How many subnets? Since 192 is 2 bits on
  (11000000), the answer is 22 2 2
• 2) How many hosts per subnet? We have 6 host bits
  off (11000000), so the equation would be 26 2
  62 hosts.

33
Example 1 (cont.)

• 3) What are the valid subnets?
• 256-192 64, which is the first subnet and also
  the block size. Keep adding the block size to
  itself until you reach the subnet mask. 64 64
  128. 128 64 192, which is invalid because it
  is the subnet mask (all subnet bits turned on).
  Our two valid subnets are, then, 64 and 128.

34
Example 1 (cont.)

• 4) Whats the broadcast address for each subnet?
• The number right before the value of the next
  subnet is all host bits turned on and equals the
  broadcast address.
• 5) What are the valid hosts?
• These are the numbers between the subnet and
  broadcast address.

35
Example 1 Final Result
36
Class C Example 2

• Network address 192.168.10.0
• Subnet mask 255.255.255.224
• Follow preceding example. Answers

37
Subnetting in Your Head

• Host address 192.168.10.33
• Subnet mask 255.255.255.240
• What subnet and broadcast address is the above IP
  address a member of?
• First, answer question 3 of the big 5
• 3) What are the valid subnets?
• 256 240 16. 16 16 32. 32 16 48. The
  host address is between the 32 and 48 subnets.
  The subnet is 192.168.10.32, the broadcast
  address is 192.168.10.47, and the valid host
  range is 192.168.10.33 192.168.10.46

38
Calculating Class B Addresses

• Network address 172.16.0.0
• Subnet mask 255.255.192.0
• Answer the five questions
• Subnets? 22 2 2. (192 11000000)
• Hosts? 214 2 16,382. (6 bits in the third
  octet, and 8 in the fourth.)
• Valid subnets? 256 192 64.
• 64 64 128. (these are the 2 subnets as
  stated in question 1.)

39
Class B Example (cont.)

• 4) Broadcast address for each subnet?
• See table.
• 5) Valid hosts? See table.

40
Class B, Example 2

• Network address 172.16.0.0
• Subnet mask 255.255.240.0
• Follow prior questions. (240 11110000)
• The table shows first three subnets, valid hosts,
  and broadcast addresses in a Class B
  255.255.240.0 mask

41
Subnetting in Your Head, Class B

• Q What subnet and broadcast address is the IP
  address 172.16.10.33 255.255.255.224 a member of?
• A 256 224 32. 32 32 64.
• 33 is between 32 and 64. However, remember that
  in Class B addresses the third octet is
  considered part of the subnet, so the answer
  would be the 10.32 subnet.
• The broadcast is 10.63, since 10.64 is the next
  subnet.

42
In Your Head, Class B Ex. 2

• Q What subnet and broadcast address is the IP
  address 172.16.90.66 255.255.255.192 a member of?
• A 256 192 64. 64 64 128. The subnet is
  172.16.90.64. The broadcast must be
  172.16.90.127, since 90.128 is the next subnet.

43
Subnetting Class A Addresses

• Same procedure as with Class B and Class C only
  you must take into account the 8 additional bits
  from the second octet.

44
Class A Example

• Network 10.0.0.0
• Subnet mask 255.255.0.0 ( /16 16 bits on)
• Subnets? 28 -2 254.
• Hosts? 216 2 65,534.
• Valid subnets? 256 255 1, 2, 3, etc. (all in
  the second octet). The subnets would be 10.0.0.0,
  10.2.0.0, 10.3.0.0, etc., up to 10.254.0.0.

45
Class A Example (cont.)

• 4) Broadcast address for each subnet?
  10.1.255.255, 10.2.255.255, etc., up to
  10.254.255.255.
• 5) Valid hosts? See table.

46
Appendix(will be added shortly)

• Hex to Binary to Decimal Conversion
• Slash Notation (/) Tables
• Boolean/Binary Calculation Method