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## PowerPoint Slideshow about ' Subnetting' - yuma

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Index

- IP addressing classes
- Subnet masking
- Subnetting
- Exercises
- ANDing function

Intro Subnetting

- IP addressing
- Classes within IP
- Class A - 16,777,214 (224 - 2) - Governments - start with 0
- Class B - 65,534(216 -2) - Medium-size companies - start with 10
- Class C - 254 (28 -2) - all other entities - start with 110
- Class D - reserved for use by Multicast services provided by The internet Group Management Group (IGMP) - start with 1110
- Multicast broadcasts allow IP datagrams to be sent to specific groups that belong to a multicast group
- Class E- Not in use or only used for testing and development Reserved for future use - start with 11110

IP Addressing

193.32.2.0

- We need to use bits from the host part of an IP address to create subnets
- The number of bits depend on the number of subnets needed for that company

Network Host

Subnet Mask

- Properties of the Subnet mask are
- 32 bits
- in binary format
- expressed as 4 octets
- Defined from left to right

- Used by internetworking devices to find out what type of network/ subnetwork is installed/used by a company

Subnet Mask

- “ The most misunderstood part of IP addressing”
- DO not introduce above in a class !
- Subnet Masks are used to make it easy to distinguish between network and host address
- example a class B network not subnetted
- 130.12.0.0 - IP address
- 255.255.0.0 - Subnet mask
- N NH H All network bits assigned to 1
- 11111111.11111111.0.0

Subnet Mask

- Default Subnet masks
- Class A - 255.0.0.0
- Class B - 255.255.0.0
- Class C - 255.255.255.0

- What happens when we use subnetting?

Subnetting

- Why ? - Because using natural address masks are not efficient - too large
- Reduces the size of the network, which in turn makes it easier to manage and troubleshoot
- Breaking up the address space into useable subnets
- Process involves borrowing bits from the host part of the address to create a larger network address
- Subnetting is done by network administrator

Subnetting Exercise A

- Example of Subnetting
- The Network Administrator of LYIT receives new Network address 132.8.0.0
- LYIT has 8 departments
- A number of questions that need to be answered are:-
- 1. What class is the network address?
- 2. How many subnets are needed?
- 3. How many bits are borrowed from the host part of the address?
- 4. How many subnets are defined and how many of these are useable?
- 5. What is the default subnet mask?
- 6. What is the new customised subnet mask?
- 7. What is the decimal value of each subnet?
- 8. What is the total number of hosts?

Subnetting

- 1. What class is the network address?
Ans. It’s a Class B address

- 2. How many subnets are needed?
Ans. 8 departments so we need 8 subnets

- 3.How many bits need to be borrowed?
Ans. 4 bits to provide 14 subnets

- 4. How many subnets are defined and how many of these are useable?
Ans. 2 x 2 x 2 x 2 = 16 are defined

16 - 2 = 14 are useable

- 5. What is the default subnet mask?
Ans. 255.255.0.0 or 11111111.11111111.0.0

Subnetting

- 6. What is the new customised subnet mask?
Ans. 128+64+32+16 = 1111 starting with the leftmost significant bit value of the leftmost host octet

255.255.240.0 or 11111111.11111111.11110000.00000000

- 7. What is the decimal value of each subnet?
Ans. 138.8.0.0

10001010.00001000.00010000.00000001

to and including

10001010.00001000.11100000.11111110

138.8.16.1 - 138.8.31.254 - subnet 1

138.8.32.1 - 138.8.47.254 - subnet 2

138.8.48.1 - 138.8.63.254 - subnet 3

etc

138.8.208.1 - 138.8.223.254 - subnet 14

Network, Subnet and Host

Subnetting

- 8. What is the total number of hosts?
14 subnets

The remainder of the host part of the address is 12 bits

we have 16-4 borrowed = 12 bits left for hosts

each subnet can have 2 to the power of 16 -2 hosts

- 212 -2 = 4094
- -2 for network and broadcast addresses
- 14 useable subnets x 4094 useable host addresses
- Ans. 57316

Subnetting Exercise B

- What would be the case if the Network Administrator were given the following network address 192.12.8.0, and the number of departments were 7.
- 1. What class is the network address?
- 2. How many subnets are needed?
- 3. How many bits are borrowed from the host part of the address?
- 4. How many subnets are defined and how many of these are useable?
- 5. What is the default subnet mask?
- 6. What is the new customised subnet mask?
- 7. What is the decimal value of each subnet?
- 8. What is the total number of hosts?

Subnetting

- 1. What class is the network address?
- Class C as it is above 191

- 2. How many subnets are needed?
- 7 subnets -why not use just 3 bits

- 3. How many bits are borrowed from the host part of the address?
- 4 bits are needed

- 4. How many subnets are defined and how many of these are useable?
- 2 x 2 x 2 x 2 = 16 are defined - 16 - 2 = 14 are useable

- 5. What is the default subnet mask?
- 255.255.255.0 class C

- 6. What is the new customised subnet mask?
- 255.255.255.240

Subnetting

- 7. What is the decimal value of each subnet?
- 192.12.8.0
- 11000000.0001100.00001000.00010000
- to and including
- 11000000.0001100.00001000.11111110
- 192.12.8.16 - 192.12.8.31 - subnet 1
- 192.12.8.32 - 192.12.8.47 - subnet 2
- 192.12.8.48 - 192.12.8.63 - subnet 3
- etc
- 192.12.8.208 - 192.8.223 - subnet 14
8. What is the total number of hosts?

- 14 x (24 -2 = 14)
- 14 x 14 = 196
Network, Subnet and Host

ANDing function

- In order to route a data packet, the router must first determine the destination network/subnet address by performing a logical AND using the destination host's IP address and the subnet mask. The result will be the network/subnet address.

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