Subnet:
Segmenting a substantial network
into many small networks to maintain the security. Example: Consider a school named “ABCD” assume there are 1000 student studying. Imagine if all the students have been put in a same hall what will happen? In that case it will be is very difficult to manage, so they have divided single classroom into 10(for example) In this case it becomes much easier to maintain for the management.
Note: In this blog we will focus more on Classful addressing
Types of Subnet:
Class A (255.0.0.0)
Class B (255.255.0.0)
Class C (255.255.255.0)
What is 255.X.X.X? It known as Subnet
mask
What is subnet mask?
Note:
What is meant by Network address and
host address?
Router forwards the packet based on
the network ID or network address. Router consist of
the Routing table, in that table it stores the Network
address, IP Address and subnet mask .example:
Imagine Device A (10.0.0.1) needs to communicate
with Device B (12.0.0.1) due to the different network the
router needs to communicate once the packet
is received, the router cross checks with the routing
table and do Bitwise AND operation.
Router takes the destination IP address and subnet
mask and do bitwise AND operation were you get the Network ID which that IP
address belong to
Why bitwise AND operation? Then only router knows
destination IP address and forward that to the packet.
If subnet mask (255.255.255.0) convert into binary we
get
255.255.255.0 = 11111111.11111111.11111111.00000000
12.0.0.1
= 00001010.0000000.00000000.00000001
If we do bitwise AND operation we get
00001010.00000000.00000000.00000000(12.0.0.0).
12.0.0.0 is a network id,
and router transfer the packet to that network device based on that network
Note: In subnetting first
IP address is network address or subnet ID or network ID and last address is
Broadcast address.
Subnet ex in networking field:
Consider on large organization were it contains 4 department (Testing, developing, maintaining, and networking.)
Why we need to split the network (emoji)? A Class consists of 2^24 host address (16777216).Imagine that can we maintain a network in that case subnetting is the best solution.
Class A: 2^24 (consist 16777216 host or
device).
Class B: 2^16(consist 65536 host or device).
Class C: 2^8 (consist 256 host or device)
Fixed length subnet mask:
Till now we focused only
on fixed
length subnet mask
What is fixed length subnet mask? In Image 2 we find 4 subnets and all networks are in the same size Here are some examples,
In this example we consider Class C as an example:
IP address: 120.1.2.0 and subnet mask is
Class C
In Image: 4
Range for departments are:
Testing department is (120.1.2.1 to 120.1.2.62)
Development department is (120.1.2.65 to 120.1.2.126)
Tech department
(120.1.2.129 to 120.1.2.190)
Networking
department is (120.1.2.193 to 120.1.2.254)
Note: Range indicates the number of devices
Totally we have 64 host (number of devices) IP address
in each part (department)
Note: from image: 3 Subnet of 4 network , are similar
therefore it known as fixed length subnet mask.
Variable length subnet mask:
Imagine in our organization there is only three
department (Testing, Development, and Networking).
To provide flexibility to network
Note: Whenever subnet size are different every subnet
gets different subnet mask
In Image: 6
Range for
Testing department is (120.1.2.1 to 120.1.2.126)
Development department is (120.1.2.129 to 120.1.2.190)
Networking
department is (120.1.2.193 to 120.1.2.254)
Conclusion:
Difference between fixed and variable length subnetting:
·
Subnet length is not fixed,
in variable length subnet masking
These two methods is also
called as a Classful addressing.
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