Fixed Length Subnet Masking (FLSM)

[@thelegend8798]

00:06 Learn about FLSM and VLSM
01:24 Assigning IP addresses requires communication between interfaces
02:50 Six networks with varying host requirements need IP addresses assigned
04:11 Class C network is suitable for maximum 20 hosts
05:33 Using fixed-length subnet masking leads to wastage of IP addresses
07:02 Subnetting in classless world
08:18 Classless addressing minimizes IP address wastage
09:32 Migrate towards VLSM to handle IP wastage effectively

[@ezramngondo8668]

Thanks a lot. Your videos are really helpful

[@md.ifthahossainsagar5679]

Thank you very much.

[@khaykhun]

Thanks

[@christianvillegas1215]

I didn't get it , Do u mean , Mask FLSM its classfull or classless?

[@azizulhakimbappy3253]

[@umer_c0des330]

In class C, we can only change host bits. Then, why are you changing network bits (3rd octet). ?

[@sajidali_6567]

he is discussing classless addressing

[@omsgaming454]

because there are 6 networks

[@DhavalAhir10]

## With Classful Approach:
Rules:
- Follow the class of the IP address.
- Use the default subnet mask for Class C: /24 (255.255.255.0).
- The first 3 octets remain unchanged within the network, according to the old classful addressing rule.
- Only the 4th octet can vary within the network to provide host IP addresses.
```
Example:
192.168.1.0 - 192.168.1.255 /24
192.168.2.0 - 192.168.2.255 /24
192.168.3.0 - 192.168.3.255 /24
```
Cons:
- Significant waste of private IP addresses.
- If a network needs only 40 IPs, then 214 IPs (254-40) are wasted.
## With Classless Approach (modern, after 1993):
CIDR is used in two main approaches for subnetting:
1. Fixed-Length Subnet Masking (FLSM)
2. Variable-Length Subnet Masking (VLSM)
Rules:
- Ignore the IP’s class.
- Ignore the default subnet mask as per the IP’s class.
- This approach uses block (chunk) subnetting.
```
Example:
192.168.1.0 - 192.168.1.63 /26
192.168.1.64 - 192.168.1.127 /26
192.168.1.128 - 192.168.1.191 /26
```
Note: The example above uses a classless approach with Fixed-Length Subnet Masking (FLSM).
Pros:
- Creates chunks based on the required number of hosts.
- Minimizes the waste of private IP addresses per network (though some waste remains).
Variable-Length Subnet Masking (VLSM) is the most efficient subnetting approach under the new CIDR rules.