Subnetting (Solved Problem 6)
Summary
TLDRThis educational video script explains how to determine the limited broadcast address in a subnet using two methods. First, it introduces the reverse engineering method, starting with a Class B subnet mask of 255.255.0.0, and identifying the network and broadcast addresses for the subnet. The second method involves a bitwise OR operation after taking the one's complement of the subnet mask. The script uses the example of an IP address 25.34.12.56 with a /16 subnet mask to demonstrate the process, resulting in a broadcast address of 25.34.255.255. The lecture concludes with a homework question involving an IP address range and asks viewers to find the broadcast address.
Takeaways
- 😀 The video script discusses subnetting, specifically finding the broadcast address in a block of addresses.
- 🔍 The example uses an IP address of 25.34.12.56 with a subnet mask represented in slash notation as /16.
- 📚 The subnet mask /16 is equivalent to 255.255.0.0 in decimal, which is a Class B subnet mask.
- 👉 The reverse engineering method starts with the subnet mask and involves converting it into binary to find the network range.
- 💡 The first subnet range is calculated to be from 25.34.0.0 to 25.34.255.255, using the subnet mask.
- 🎯 The given IP address falls within the first subnet, and the last address of this subnet is the broadcast address.
- 🛠️ For finding the broadcast address, a bitwise OR operation is used after taking the one's complement of the subnet mask.
- 📝 The process involves converting the IP address and the inverted subnet mask into binary and performing the OR operation.
- 🔢 The result of the OR operation gives the broadcast address in binary, which is then converted back to decimal to find 25.34.255.255.
- 📚 The video also mentions a homework question asking to find the broadcast address for an IP block with an address range of 182.44.82.16-26.
- 👏 The lecture concludes with a recap of the process and an encouragement for viewers to apply the knowledge to solve the homework question.
Q & A
What is the IP address given in the script?
-The IP address given in the script is 25.34.12.56.
What is the subnet mask notation used in the script?
-The subnet mask notation used in the script is slash 16, which is equivalent to 255.255.0.0 in decimal.
What is the reverse engineering method mentioned in the script?
-The reverse engineering method starts with the subnet mask and involves converting it to binary, identifying the subnet generator, and determining the network ranges.
What is the subnet generator in the given subnet mask?
-The subnet generator in the given subnet mask is 1, and it is located in the second octet.
How is the first subnet range determined in the script?
-The first subnet range is determined by using the network address 25.34.0.0 and the broadcast address 25.34.255.255.
What is the difference between finding the network address and the broadcast address in terms of bitwise operations?
-For finding the network address, a bitwise AND operation is used, whereas for finding the broadcast address, a bitwise OR operation is used after performing the subnet mask complement.
Why is the subnet mask complement necessary before finding the broadcast address?
-The subnet mask complement is necessary to convert all ones to zeros and all zeros to ones in the subnet mask, which is then used in the bitwise OR operation to determine the broadcast address.
What is the broadcast address of the subnet where the given IP address resides?
-The broadcast address of the subnet where the given IP address 25.34.12.56 resides is 25.34.255.255.
How does the bitwise OR operation work in determining the broadcast address?
-The bitwise OR operation sets an output bit to 1 if at least one of the input bits is 1, resulting in the broadcast address when applied to the IP address and the complemented subnet mask.
What is the homework question presented in the script?
-The homework question asks to find the last address, which is the limited broadcast address, in a block of addresses where the IP address of one host is 182.44.82.16-26.
Outlines
🔍 Reverse Engineering to Find Broadcast Address
The video script begins with an exploration of subnetting, specifically focusing on identifying the broadcast address for a given IP address and subnet mask. The IP address provided is 25.34.12.56, and the subnet mask is represented in slash notation as /16, which translates to 255.255.0.0 in decimal. The method used to find the broadcast address involves reverse engineering, starting with the subnet mask and converting it into binary to determine the network's range. The first subnet is identified as 25.34.0.0 to 25.34.255.255. The script explains that the last address in this range, 25.34.255.255, is the broadcast address for the subnet. Additionally, a formal method is introduced, which involves using a bitwise OR operation after taking the one's complement of the subnet mask. This process is crucial for understanding how to calculate the broadcast address in networking.
📚 Step-by-Step Guide to Calculate Broadcast Address
The second paragraph of the script provides a step-by-step guide on how to calculate the broadcast address using the bitwise OR operation. It starts with taking the given IP address, converting it into binary, and then bringing in the subnet mask, which is /16 or 255.255.0.0. The key step introduced here is the one's complement of the subnet mask, which involves inverting all bits (changing 1s to 0s and vice versa). This complemented subnet mask is then used in the bitwise OR operation with the binary representation of the IP address to find the broadcast address. The operation is explained with examples, demonstrating how the presence of a '1' in either input results in a '1' in the output. The final result of this operation for the given IP address is 25.34.255.255, confirming the broadcast address. The script concludes with a homework question that asks the viewer to find the broadcast address for a different IP address range, 182.44.82.16-26, encouraging practical application of the concepts learned.
Mindmap
Keywords
💡Subnetting
💡IP Address
💡Subnet Mask
💡Slash Notation
💡Broadcast Address
💡Reverse Engineering Method
💡Class B Subnet Mask
💡Bitwise AND Operation
💡Bitwise OR Operation
💡One's Complement
💡Homework Question
Highlights
The lecture discusses finding the limited broadcast address in a subnet using the reverse engineering method.
An example IP address 25.34.12.56 and subnet mask in slash notation /16 is used to illustrate the process.
The subnet mask is a Class B subnet mask, represented as 255.255.0.0 in decimal.
Binary conversion of the subnet mask reveals all ones in the first two octets and all zeros in the last two.
The subnet generator is identified as 1 in the second octet, with a decimal place of one.
Network ranges are created using the subnet generator and octet position, with the first subnet being from 25.34.0.0 to 25.34.255.255.
The given IP address falls within the first subnet, with the first address being the network address and the last being the broadcast address.
The broadcast address for the subnet is determined to be 25.34.255.255.
A formal method for finding the broadcast address involves using the bitwise OR operation.
Before the OR operation, the subnet mask must be inverted (ones complement) to find the broadcast address.
The bitwise OR operation is explained, where an output of one is produced if at least one input is one.
The process of converting the binary result back to decimal to find the broadcast address is demonstrated.
The importance of the subnet mask complement step before the OR operation is emphasized.
A homework question is presented, asking to find the broadcast address for an IP block with a given host IP address.
The lecture concludes with a summary of the steps and a reminder of the importance of the subnet mask complement.
The lecture includes a musical and applause segment, indicating the end of the presentation.
Transcripts
foreign
number six in subnetting
in a block of addresses we know the IP
address of one host is
25.34.12.56 and the subnet mask is
represented in a slash notation which is
slash 16. what is the last address that
is the limited broadcast address in this
block we have already solved this in the
previous lecture but in the previous
lecture we had intended to find the
network address but we are required to
find the broadcast address in this
lecture let's solve this first with the
reverse engineering method which we had
dealt in the previous case the reverse
engineering method starts with the
subnet mask we know the subnet mask is a
Class B subnet mask which is
255.255.0.0 when we convert this subnet
mask into binary we will be getting all
ones in the first two octets and all
zeros in the next two octets then where
is the first one we are encountering the
first one we are encountering in the
second octet right so in the second
octet the first one is here and what is
the decimal place of this first one when
we move from right to left the decimal
place of this one is exactly one so the
subnet generator is 1 and the octet
position is 2 right because this subnet
generator is in the second octet so the
subnet generator is equal to 1 and the
octet position is equal to 2 and we have
already created this network ranges I
had just copied from the previous
problem and I will paste it here we know
the first Subnet will be from 25 or
34.0.0 to
25.34.255.255 if you want to know how I
have generated this I request you to
watch the previous problem that is
solved problem number five now the IP
address which is mentioned in the
question is falling in the first Subnet
we know the first address is the network
address and the last address of the
subnet is the broadcast address so
obviously 25 or
34.255.255 is the broadcast address of
this subnet the IP address of one of the
hosts is given in the question and we
found out the broadcast address of this
entire net work right this is one way of
solving this and this way of solving the
problem is the reverse engineering
approach now we will solve this in a
formal way in the previous lecture we
have found the network address by using
a simple and operation that is the
bitwise and operation but for finding
the broadcast address in this problem we
are going to use the bitwise or
operation just see how I am going to do
this so first we need to take the IP
address which is given in the question
right the IP address which is given in
the question is 25 or
34.12.56 as usual we need to convert
this IP address into binary and we
converted this into binary now we need
to bring in the subnet mask and what is
this update mask that is mentioned in
this question
class 16 right slash 16 means we need to
fill in 16 ones here and then remaining
zeros let's fill that so we are bringing
in 16 ones here and 16 zeros here
because this is the slash 16 subnet mask
and the equivalent of slash 16 in
decimal is
255.255.0.0 in the previous problem we
just did and operation with these values
right now here one additional step the
additional step is before making the or
operation we need to do the mass
complement so this is the subnet mask we
need to do the subnet mask complement
complement means it's simple once
complement so here we will convert all
ones as zeros and all zeros as ones so
when we do that we'll be getting the
first two octets with full of zeros and
the last two octets is full of one
please note I am pinning this step here
it's a very important step we need to do
subnet mask complement before
progressing with the or operation in the
previous problem when we did a network
address calculation we didn't do this
complement operation simply we have
taken the IP address subnet mask
converted that into binary and performed
the bitwise and operation but here we
need to take the IP address first and
then we need to take the subnet mask and
then inverse the subnet mask that is
make one's complement to the subnet mask
so this is a very important step the
step is mass complement after we
complete this Mass complement as usual
we will start proceeding with the
operation the operation for finding the
broadcast address is the bitwise or
operation please note for finding the
network address we did and operation for
finding the broadcast address we need to
perform or operation now we will carry
out the bitwise or operation the bitwise
or operation is very simple when any one
of the inputs is one we will be getting
one as the output so if both the inputs
are 0 we'll be getting 0 as the output
for 0 0 will be getting 0 0 1 1 0 1 1
for these combinations will be getting
1. in this case we'll be getting this as
the result let's check it out now so
let's take the first octet and we'll
verify it so for 0 0 we'll be getting 0
for 0 0 it's zero zero zero it's zero
one zero it's one any one of the inputs
is high right so 1 0 it is one zero zero
it is 0 and 1 0 it is one right we will
take the third octet and verify it the
third octet we can see at least one of
the inputs is one right first four
places are zero in the IP address part
but fortunately we are having four ones
in the Subnet Mask Part the next two
bits are one here as well as here and
the next two bits are zero in the IP
address bar but one in the Subnet Mask
Part so at least one input is one in
this case
so we had just performed the bitwise or
operation now let's convert this octet
into decimal and when we convert this
octet into decimal we'll be getting 25
or
34.255.255 so this is the broadcast
address again I repeat when you are
intended to find the broadcast address
please ensure this step after converting
the subnet mask into binary do one's
complement and that's it guys before we
conclude let's see the homework question
the question is in a block of addresses
we know the IP address of one host is
182.44.82.16-26 what is the last address
that is the limited broadcast address in
this block so you are required to find
out the broadcast address
and that's it guys I hope you enjoyed
this lecture and thank you for watching
[Music]
[Applause]
[Music]
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