`Subnetting
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Transcript of `Subnetting
Raees KhanSession Type: SeminarLanguage: Urdu & English Session Duration: 2 Hours
BSC (Hons) Computer SciencesMCSE, RHCT, CCNA, CCNP, MPLShttp://[email protected]
IPv4 Subnetting
CIDRNotation
Subnetting Process
IPv4 Subnetting
AGENDA
Subnetting Pre-requisite
IP Addressing Basics
What is Internet Protocol (IP).
IP usage and it characteristics.
IP Address Format: Dotted Decimal Notation.
IP Address Classes: Identification of class of an IP address.
IP Address Ranges for Class A, B , and C.
Private Addresses and Public Addresses.
Finding the Network address, Broadcast address, valid range of IPs.
Understanding masks and how to use them.
IP Addressing Table
• What is Subnetting and why do we do it.
• Getting acquainted with CIDR notation.
• Writing Subnet Mask.
• Learn Subnetting–Finding Network Addresses–Finding Broadcast Addresses–Finding Valid ranges of IPs .
AGENDA
%
DefiningSubnetting
Defining Subnetting
• Subnetting is the concept of dividing the network into smaller portions called subnets.
• This is done by borrowing bits from the host portion of the IP address, enabling more effi cient use of the network address.
Why Subnetting ?
• S u b n e t t i n g l e t s y o u a l l o c a t e a d d r e s s e s b y t a k i n g o n e l a r g e b r o a d c a s t d o m a i n a n d b r e a k i n g i t u p i n t o s m a l l e r m o r e m a n a g e a b l e b r o a d c a s t d o m a i n s .
• E ffi c i e n t u s e o f N e t w o r k a d d r e s s e s b y d i v i d i n g a n e t w o r k i n t o s u b - n e t w o r k s .
• R e s t r i c t B r o a d c a s t t r a ffi c ( V l a n s )
• S i m p l i fi e d A d m i n i s t r a t i o n
CIDR Notation
• T h e m e t h o d t h a t I S P s ( I n t e r n e t S e r v i c e P r o v i d e r s ) u s e t o a l l o c a t e a n a m o u n t o f a d d r e s s e s t o a c o m p a n y , a h o m e .
• E x a m p l e : 1 9 2 . 1 6 8 . 1 0 . 3 2 / 2 8
• T h e s l a s h n o t a t i o n ( / ) m e a n s h o w m a n y b i t s a r e t u r n e d o n ( 1 s )
• T h e v a l u e a f t e r s l a s h r e p r e s e n t s n e t w o r k b i t s .
CIDR Notation
CIDR Notation
In CIDR notation, the block granted is defined by the first address and the prefix length.
Also known as Prefix Notation OR Slash Notation
WritingSubnet Mask
128 64 32 16 8 4 2 1 SUM
0 0 0 0 0 0 0 0 0
1 0 0 0 0 0 0 0 128
1 1 0 0 0 0 0 0 192
1 1 1 0 0 0 0 0 224
1 1 1 1 0 0 0 0 240
1 1 1 1 1 0 0 0 248
1 1 1 1 1 1 0 0 252
1 1 1 1 1 1 1 0 254
1 1 1 1 1 1 1 1 255
Nine Possible Values for Subnet Mask
VALUE
OCTET
0 128 192 224 240 248 252 254
2nd 8 9 10 11 12 13 14 15
3rd 16 17 18 19 20 21 22 23
4th 24 25 26 27 28 29 30 31
Placing Values in right Octet
Subnet Mask CIDR Subnet Mask CIDR
255.0.0.0 /8 255.255.252.0 /22
255.128.0.0 /9 255.255.254.0 /23
255.192.0.0 /10 255.255.255.0 /24
255.224.0.0 /11 255.255.255.128 /25
255.240.0.0 /12 255.255.255.192 /26
255.248.0.0 /13 255.255.255.224 /27
255.252.0.0 /14 255.255.255.240 /28
255.254.0.0 /15 255.255.255.248 /29
255.255.0.0 /16 255.255.255.252 /30
255.255.128.0 /17 255.255.255.254 /31
255.255.192.0 /18 255.255.255.255 /32
255.255.224.0 /19
255.255.240.0 /20
255.255.248.0 /21
Writing Subnet Mask
Default Mask Vs Subnet Mask
A Default/Subnet mask defi nes which portion of the address is used to identify the network and which denotes the hosts.
Subnetting
Formulas used in Subnetting
Number of subnets = 2x
Where x = number of bits borrowed
Possible number of subnets are 2, 4, 8, 16, 32, 64…
Block Size = Total number of Address Block Size = 256-Mask
Number of valid IPs = 2y-2 Where y = number of 0’s
Subnetting Example
Question: Perform 1 bit subnetting and write Network ID, Broadcast ID, and valid range of IPs in each subnet.
In practical terms, the subnet mask actually conveys only a single piece of information: where the line is drawn between the subnet ID and host ID
Answer: The /24 represents the network bits so you cannot change these bits in subnetting. Borrow one bit from host bits to perform subnetting.
Given that 192.168.1.0 /24
192 . 168 . 1 . 0
11000000 . 10101000 . 00000001 . 0 0000000
192 . 168 . 1 . 0
11000000 . 10101000 . 00000001 . 0 0000000
1
Draw a line after 24 bits because they can’t be changed. Make the combinations with subnetting bits.
The two combinations are actually two subnets.
Subnetting Example
1
11000000 . 10101000 . 00000001 . 0000000
The two subnets are
192 . 168 . 1 . 0
192 . 168 . 1 . 128
/25
/25
For the first subnet 192.168.1.0/25The Net ID is 192.168.1.0The Valid range of IPs is 192.168.1.1 – 192.168.1.126The Broadcast ID is 192.168.1.127
For the Second subnet 192.168.1.128/25The Net ID is 192.168.1.128The Valid range of IPs is 192.168.1.129 – 192.168.1.254The Broadcast ID is 192.168.1.255
Subnetting Example Converting binary into decimal and writing custom subnet mask.
IP addressing conventions reserve two IP addresses per subnet.
• Subnet Address / Network ID– IP address that has al l binary 0s in
the host fi eld
• Broadcast Address– IP address that has al l binary 1s in
the host fi eld
Reserved IP Addresses per Subnet
Possible Subnets and Hosts for a Class A Network
Possible Subnets and Hosts for a Class B Network
Possible Subnets and Hosts for a Class C Network
Food for Thought
Subnet Mask or Custom subnet mask tells us that how many bits are used for Subnet ID portion and how many for host ID portion. Identify how many bits are used for subnetting in the following IP address using its subnet mask:
1.IP Address: 139.65.225.4 Subnet Mask: 255.255.224.0 2.IP Address: 139.65.225.4 Subnet Mask: 255.255.248.0 3.IP Address: 201.35.20.18 Subnet Mask: 255.255.255.128 4.IP Address: 201.35.20.18 Subnet Mask: 255.255.255.240 5.IP Address: 190.47.115.6 Subnet Mask: 255.255.128.0
Question 1
Question 2
Find the following:Number of Network bitsNumber of Host bitsNumber of Subnet bitsNumber of SubnetsNumber of Hosts per Subnet
For 8.1.4.5/16 130.2.140.100/24 198.190.100.61/26
Suppose you have a class B Network 172.121.0.0. Yourtask is to design a subnet scheme so that we can create 64 Network segments (subnets) within this Network.
1. How many bits would you use for the subnet ID?
2. How many bits would you use for the Host ID?
3. How many maximum possible subnets wil l be there?
4. How many maximum possible hosts wil l be there in each subnet?
5. Write down the Subnet Mask of your scheme.
6. Write down the fi rst val id IP address, last val id IP address and the broadcast address of the Third subnet of your scheme.
Question 3
