Classless Addressing (Part 1)

Summary

This lecture discusses the limitations of classful IP addressing, which categorizes addresses into five classes and often leads to IP address wastage. It highlights the drawbacks, such as lack of flexibility, inefficient address use, and increased routing table entries, which necessitate the transition to classless addressing. Classless addressing allows for a more efficient and flexible allocation of IP addresses based on actual network requirements, reducing waste and improving routing performance.

Takeaways

• 📚 Classful addressing in IPv4 is divided into five classes: A, B, C, D, and E, with A, B, and C being the most commonly used for general purposes.
• 🚀 In classful addressing, a Class C network can support up to 254 hosts, but if more hosts are needed, a larger class like B is required, which can support up to 65,534 hosts.
• 🔢 The script highlights a specific example where a requirement of 300 devices leads to the necessity of using Class B, resulting in the waste of 65,234 IP addresses.
• 🏢 Large organizations face the drawback of classful addressing due to the lack of flexibility in internal address allocation, as they are assigned large blocks of addresses that may not match the network structure.
• 📉 Classful addressing leads to inefficient use of address space, as only three classes are used for general purposes, and the existence of three block sizes can lead to waste.
• 🌐 The growth of the internet requires routers to handle more routing table entries, which can cause performance issues due to the proliferation of routing table entries in classful addressing.
• 🚫 One of the main drawbacks of classful addressing is the lack of internal address flexibility, inefficient use of address space, and the increase in routing table entries.
• 🔄 The transition from classful to classless addressing is necessary to address the issues of IP address wastage and routing table inefficiencies.
• 💡 Classless addressing allows for the creation of subnet masks based on the actual needs of the network, enabling more efficient use of IP addresses.
• 🌟 In classless addressing, networks can be designed to use IP addresses sparingly, reducing waste compared to classful addressing.
• 🎓 The lecture concludes by emphasizing the understanding of the drawbacks of classful addressing and the advantages of classless addressing for efficient IP address utilization.

Q & A

What is classful addressing in IP networking?

Classful addressing refers to the system of IP version 4 (IPv4) where there are five classes of addresses: A, B, C, D, and E, with classes A, B, and C being used for general purposes. Each class has a fixed subnet mask and a maximum number of hosts it can support.

What is the maximum number of hosts that can be supported in a Class C network?

A Class C network can support up to 254 hosts.

Why might Class B addressing be inefficient for a network that requires only 300 devices?

Class B addressing is inefficient for a network requiring only 300 devices because it can support up to 65,534 hosts, which means that 65,234 IP addresses would be wasted.

What is the main drawback of classful addressing when it comes to IP address allocation?

The main drawback of classful addressing is the inefficient use of IP address space due to the fixed subnet masks and the large blocks of addresses that may not match the underlying network structure.

How does classful addressing affect the routing table entries in routers?

Classful addressing can lead to the proliferation of routing table entries as routers need to store more entries to handle the routing of IP datagrams, which can cause performance problems.

What is the maximum number of hosts that can be supported in a Class A network?

A Class A network can support 1,677,214 hosts.

How does classless addressing address the issue of IP address wastage compared to classful addressing?

Classless addressing allows for the creation of custom subnet masks and more efficient use of IP addresses based on the actual requirements of the network, thus reducing wastage.

What is one of the main benefits of classless addressing over classful addressing?

One main benefit of classless addressing is the lack of internal address flexibility, allowing for a better match between the assigned address blocks and the structure of the underlying internal network.

Why is it necessary to migrate from classful to classless addressing?

It is necessary to migrate from classful to classless addressing to address the drawbacks of classful addressing, such as lack of flexibility, inefficient use of address space, and the proliferation of routing table entries.

Can you give an example of how classless addressing allows for more efficient IP address usage?

In classless addressing, if a network requires only 25 computers, it can create a custom subnet mask that allows for exactly 25 usable IP addresses, thus avoiding the wastage of addresses that would occur with classful addressing.

What is the impact of classless addressing on the size of routing tables in routers?

Classless addressing can potentially reduce the size of routing tables by allowing for more efficient allocation of IP addresses, which in turn can reduce the number of entries required in routing tables.

Outlines

00:00

📚 Introduction to Classful Addressing Drawbacks

This paragraph introduces the concept of classful addressing in IPv4, highlighting its limitations and inefficiencies. It explains the five classes of IPv4 addresses (A, B, C, D, and E), with a focus on A, B, and C for general use. The speaker illustrates the issue of IP address wastage by providing examples, such as needing a Class B network for 300 devices when Class C would suffice, resulting in the waste of 65,234 IP addresses. The paragraph also discusses the lack of address flexibility for large organizations and the inefficient use of the limited IP address space due to the existence of three block sizes. Furthermore, it touches on the proliferation of routing table entries as a performance issue for routers, emphasizing the need to transition from classful to classless addressing to conserve IP addresses and improve network efficiency.

05:01

🚀 Transition to Classless Addressing

The second paragraph delves into the migration from classful to classless addressing, emphasizing the benefits of the latter. Classless addressing allows for a more efficient and flexible use of the IP address space, enabling the creation of subnet masks tailored to the specific needs of a network. The speaker provides an example where a network with only 25 computers can be designed with a custom subnet mask, thereby sparingly using IP addresses. This method contrasts with classful addressing, which does not allow for such customization and leads to significant IP address wastage. The paragraph concludes by summarizing the drawbacks of classful addressing and the advantages of classless addressing, encouraging the adoption of the latter for better IP address management and network design.

Keywords

💡Classful Addressing

Classful addressing refers to the traditional method of IP address allocation in IPv4, where addresses are divided into five classes (A, B, C, D, and E), each with a predefined network mask. This system was designed to simplify the allocation of IP addresses but often led to inefficiencies due to the fixed size of the network mask. In the video, classful addressing is criticized for its inflexibility and waste of IP addresses, as it does not allow for the precise allocation of addresses based on the actual needs of a network.

💡Classless Addressing

Classless addressing, also known as CIDR (Classless Inter-Domain Routing), is a more flexible method of IP address allocation that overcomes the limitations of classful addressing. It allows for variable-length subnet masks, enabling a more efficient use of the available IP address space. The video emphasizes the need for classless addressing to replace classful addressing due to its ability to conserve IP addresses and adapt to the varying requirements of different networks.

💡IPv4

IPv4, or Internet Protocol version 4, is the fourth version of the Internet Protocol used to identify devices on a network and establish connections. It is the most widely used version and is characterized by its 32-bit address scheme, which allows for approximately 4.3 billion unique addresses. The video discusses the limitations of IPv4's classful addressing system and the transition to classless addressing to better manage the finite number of IPv4 addresses.

💡Subnet Mask

A subnet mask is a 32-bit number that separates the network portion of an IP address from the host portion. In classful addressing, subnet masks are fixed and determined by the class of the IP address. The video script illustrates the inefficiency of fixed subnet masks, such as when a network requires 300 devices but a Class B address can accommodate up to 65,534, leading to a significant waste of IP addresses.

💡IP Address Waste

IP address waste occurs when more IP addresses are allocated to a network than are actually needed, leading to an inefficient use of the limited IP address space. The video script provides examples of this waste, such as when a network requires only 300 devices but is forced to use a Class B address that can accommodate 65,534, resulting in 65,234 wasted IP addresses.

💡Routing Table

A routing table is a data file used by routers to determine the best path for forwarding IP datagrams to their destination. As the internet grows, the number of routing table entries increases, which can cause performance issues for routers. The video explains that classful addressing contributes to the proliferation of routing table entries due to its inflexibility in allocating IP addresses.

💡Internal Address Flexibility

Internal address flexibility refers to the ability of an organization to allocate IP addresses in a manner that best suits its internal network structure. The video script points out that classful addressing lacks this flexibility because it assigns large, monolithic blocks of addresses that may not align with the actual needs of an organization's network.

💡Inefficient Use of Address Space

Inefficient use of address space is a concept highlighted in the video script, referring to the unnecessary allocation of IP addresses that are not used, which is a byproduct of classful addressing. The script explains that the existence of three block sizes (Class A, B, and C) can lead to the waste of limited IP address space, which is a significant issue given the finite number of IPv4 addresses available.

💡Proliferation of Routing Table Entries

The proliferation of routing table entries is a consequence of the growth of the internet and the need for routers to store more information to efficiently route IP datagrams. The video script describes how classful addressing exacerbates this issue by not allowing for the precise allocation of IP addresses, leading to an increase in the number of routing table entries and potential performance problems for routers.

💡IP Address Allocation

IP address allocation is the process of assigning IP addresses to devices on a network. The video script discusses the inefficiencies of classful addressing in IP address allocation, where fixed subnet masks lead to over-allocation and waste. It contrasts this with classless addressing, which allows for a more precise and efficient allocation of IP addresses based on actual network requirements.

💡Network Mask

A network mask, synonymous with subnet mask, is used to define the boundary between the network and host portions of an IP address. In the context of the video, classless addressing allows for the customization of network masks, enabling more efficient and tailored allocation of IP addresses to networks of varying sizes. This is in contrast to classful addressing, where network masks are predetermined and do not allow for such customization.

Highlights

Introduction to classless addressing as an alternative to classful addressing.

Explanation of classful addressing with its five classes: A, B, C, D, and E, with A, B, and C being most commonly used.

Limitation of class C networks to 254 hosts and the need for class B for networks requiring more than 254 hosts.

Waste of IP addresses in class B networks when the requirement is less than the maximum capacity.

Class A networks catering to a vast number of hosts, but leading to IP address wastage for smaller requirements.

Drawbacks of classful addressing including lack of address flexibility and inefficient use of address space.

The impact of classful addressing on routing tables, causing performance issues for routers.

The need for migration from classful to classless addressing due to the inefficiencies and limitations of classful addressing.

Classless addressing allows for the sparing use of IP addresses based on actual network requirements.

Classless addressing reduces the wastage of IP addresses compared to classful addressing.

The ability to create custom subnet masks in classless addressing for precise network requirements.

Practical example of creating a network for 25 computers using classless addressing to avoid IP wastage.

The importance of classless addressing in conserving the limited IP address space.

Comparison of classful and classless addressing in terms of IP address conservation and network efficiency.

The conclusion emphasizing the understanding of classful addressing drawbacks and the necessity of classless addressing.

End of the lecture with a thank you note and applause.

Transcripts

in the previous lectures we have seen

classful addressing

and today we will see classless

addressing part one what we are going to

deal in part one upon the completion of

this session the learner will be able to

outcome number one we will know the

drawbacks of classful addressing and

outcome number two we will understand

the need for classless addressing let's

start with what is class full addressing

in classful ipv for addressing we have

five classes of ipv for addresses class

a b c d and e and class a b c are used

for our general purpose

suppose if we want to create a network

with 200 devices then we can obviously

go for classy any classy network can

cater up to 254 hosts

in case if our requirement is 300 so we

can't go for classy because in class c

the maximum number of hosts or devices

possible is 254 only

in order to handle 300 devices we need

to go to class b so in class b we can

have a maximum of 65

534 hosts possible per network in case

if our requirement is just 300 no other

way we need to go for class b but class

b wastes a lot of ip addresses in the

example we have taken we need to create

a network that uses 300 devices or that

contains 300 devices so obviously we

can't go for class c so we need to go to

class b but if we note in class b

it can have a maximum of 65 534 hosts or

devices or ip addresses but our

requirement is just 300 so 65 534 minus

300 is 65

234 ip addresses we are going to waste

that's a huge set of ip addresses we are

wasting

and that's the main drawback of class

full addressing

in case if we want to have a network

which needs 80 000 ip addresses so

obviously we cannot use class b so we

need to go to class a where class a is a

big number of network where it can cater

1 crore 67 lakh 77

214 hosts possible per network so

classful addressing obviously wastes ip

addresses say if i want to create a

network that needs only five devices i

need to obviously go for class c because

in a classful world class c has this

many networks wherein in each network we

can have

254 hosts but our requirement is just

five so obviously we are going to waste

249 ip addresses

let's now analyze the drawbacks of

classful addressing basically classful

addressing has the lack of internal

address flexibility big organizations

are assigned large monolithic blocks of

addresses that don't match well the

structure of the underlying internal

network so if we have a big organization

since big organization needs either

class b or class c so these block of

addresses that do not exactly match the

underlying internal network

and the second drawback is inefficient

use of address space we know there are

five classes of ipv4 addresses and we

have only three classes that are used

for our general purpose so the existence

of three block sizes may be class a b

and c leads to waste of limited ip

address space we already seen this in

the previous slide class full addressing

vs ip addresses

and also the third drawback is

proliferation of routing table entries

we know a switch is going to store the

mac address table whereas a router is

going to store the routing table routing

tables are really needed in order to

take a decision to forward the packets

as the internet grows more and more

entries are required for routers to

handle the routing of ip datagrams which

causes performance problems for routers

attempting to reduce inefficient address

space allocation leads to even more

routing table entries if we take a

router that router is also going to have

some memory and this memory is going to

store the routing table in a routing

table the ip addresses are going to be

stored what happens if the routing table

is a very big one it's getting increased

periodically router also has a limited

memory size right it can't handle all ip

addresses in the routing table so when

we go for class full addressing we have

this drawback too so basically the

drawbacks of classful addressing

includes lack of internal address

flexibility inefficient use of address

space and the proliferation of router

table entries or routing table entries

and because of these problems we need to

migrate from class full addressing to

classless addressing in a nutshell

classful addressing waste type addresses

so we need to sparingly use the ip

addresses but with classful addressing

that is with the fixed subnet mask it's

not possible to save the ip addresses so

that's why we are migrating towards

classless addressing in classless

addressing we are going to use the ip

address space sparingly and based on the

need as well suppose if we are going to

create a network which is going to have

only 25 computers we can create our own

subnet mask and we can create our own

network by sparingly used ip addresses

so sparring usage of ip address is not

possible in class full addressing

whereas it is made possible in classless

addressing classless addressing also

weighs some ip addresses but not that

much when compared to class full

addressing and that's it guys i hope now

you know the drawbacks of glassfull

addressing and we understood the need

for classless addressing

i hope you guys enjoyed the lecture and

thank you for watching

[Music]

[Applause]

[Music]

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