Lec-41: Class A in IP addressing with Example in HINDI | Classful Addressing | Network Layer

Summary

This video explains Class A IP addressing in IPv4, part of Classful Addressing, and its significance in network management. It covers the basics of IP address structure, highlighting the fixed first bit for Class A addresses and the role of the first octet as the network ID. The video explains the number of networks and hosts in Class A, the reserved addresses, and the concept of broadcast addresses. Additionally, it illustrates the process of determining network IDs using default masks. The content aims to make the topic simple and easy to understand, especially for exams like GATE or UGC-NET.

Takeaways

• 😀 Classful Addressing divides IP addresses into five classes: A, B, C, D, and E, with Class A being the focus in this video.
• 😀 IP addresses are 32 bits long in IPv4, and they are divided into four octets of 8 bits each, using Dotted Decimal Representation.
• 😀 In Class A, the first bit of the first octet is always 0, which helps identify Class A IP addresses from others.
• 😀 The number of possible Class A IP addresses is 2^31, given that the first bit is fixed to 0.
• 😀 Class A IP addresses are divided into Network ID (first 8 bits) and Host ID (remaining 24 bits). The first octet defines the network.
• 😀 The first 7 bits of the first octet in Class A can be varied, allowing 128 possible network IDs, but the first (0.0.0.0) and last (127.0.0.0) are reserved.
• 😀 The total number of usable Class A networks is 126, after excluding the reserved addresses 0.0.0.0 and 127.0.0.0.
• 😀 Each Class A network supports up to 2^24 hosts, but the first and last addresses in the network range are reserved: the first represents the network, and the last is used for broadcasting.
• 😀 Class A IP addresses have a default subnet mask of 255.0.0.0, which helps determine the network ID of an address like 64.0.0.8.
• 😀 A practical example shows that the IP address 64.0.0.0 represents the entire network for Google, and individual hosts will have IP addresses like 64.0.0.1 or 64.0.0.255 for the broadcast address.

Q & A

What is Classful Addressing in IP addressing?

Classful Addressing is a method of dividing IP addresses into five classes (A, B, C, D, and E), introduced in the 1980s. It was used to allocate IP addresses based on the size of the network and the number of hosts required. It defines specific ranges for each class of address.

Why was Classful Addressing introduced in the 1980s?

Classful Addressing was introduced due to the increasing demand for IP addresses in the 1980s. With the growth of the internet and companies needing more IP addresses, Classful Addressing allowed more efficient allocation by dividing IP addresses into different classes, catering to different network sizes.

How are IP addresses divided in Classful Addressing?

IP addresses in Classful Addressing are divided into five classes: Class A, B, C, D, and E. Each class has a specific range and is designed to accommodate different numbers of hosts and networks, depending on the class.

What is the structure of a Class A IP address?

A Class A IP address is a 32-bit address divided into 4 octets. The first octet always starts with a '0', which signifies it as a Class A address. The remaining bits are used for network and host IDs.

How many possible IP addresses exist in Class A?

Class A has 2^31 possible IP addresses because the first bit is fixed as '0' in the first octet, leaving 31 bits for variation, resulting in 2^31 addresses.

How many networks are possible in Class A, and why are two of them not used?

Class A can accommodate 128 networks, but two addresses are reserved and not used. The first address (0.0.0.0) is reserved for IANA, and the last address (127.0.0.0) is reserved for loopback and diagnostic functions. Hence, 126 networks are practically available for use.

What does the first octet of a Class A IP address represent?

In a Class A IP address, the first 8 bits of the first octet represent the network ID, while the remaining 24 bits are used for the host ID, which defines how many hosts can exist within the network.

Why is the first and last address in a Class A network not usable for hosts?

The first address in a Class A network represents the network itself and cannot be assigned to any host. The last address is reserved as the broadcast address, used for sending messages to all hosts within the network. Therefore, both addresses cannot be assigned to hosts.

What is the default subnet mask for Class A?

The default subnet mask for Class A is 255.0.0.0. This mask indicates that the first 8 bits represent the network ID, and the remaining 24 bits represent the host ID.

How can you identify if an IP address belongs to Class A?

To identify if an IP address belongs to Class A, check the first octet. If the value is between 0 and 127, it belongs to Class A. For example, IP addresses like 64.0.0.0 or 127.0.0.0 are in Class A.