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ThinkMo EDU Share – network 76.Detailed explanation of IPv4

蒂娜 No Comments 05/08/2023

ThinkMo EDU Share – network 76.Detailed explanation of IPv4

Internet Protocol version 4 (IPv4) is the fourth iteration of the Internet Protocol (IP) and is the most widely used version of the protocol to date. It was first introduced in 1981 and is still in use today, although it is being gradually replaced by IPv6. In this article, we will provide a detailed explanation of IPv4.

IPv4 Basics:

IPv4 is a connectionless protocol that operates at the network layer of the OSI model. It is responsible for the addressing and routing of data packets across a network. An IPv4 address is a 32-bit number represented in decimal notation, consisting of four octets separated by dots. Each octet represents a number between 0 and 255.

IPv4 addresses are divided into two parts: the network portion and the host portion. The network portion of the address is used to identify the network, while the host portion is used to identify the individual host on that network. The subnet mask is used to determine the size of the network and the host portion of the address.

IPv4 Address Classes:

IPv4 addresses are divided into five classes: A, B, C, D, and E. Classes A, B, and C are used for unicast addressing, while classes D and E are used for multicast and experimental addressing, respectively.

Class A addresses are used for large networks and have a subnet mask of They begin with a number between 1 and 126 in the first octet.

Class B addresses are used for medium-sized networks and have a subnet mask of They begin with a number between 128 and 191 in the first octet.

Class C addresses are used for small networks and have a subnet mask of They begin with a number between 192 and 223 in the first octet.

IPv4 Address Assignment:

IPv4 addresses can be assigned in several ways, including statically, dynamically, and through the use of Network Address Translation (NAT). Static addressing involves manually assigning a specific IP address to a device, while dynamic addressing involves the automatic assignment of IP addresses by a DHCP server.

NAT is a technique used to conserve IPv4 address space by allowing multiple devices to share a single public IP address. It involves the translation of private IP addresses to public IP addresses as packets pass through a router or firewall.

IPv4 Packet Structure:

An IPv4 packet consists of a header and a payload. The header contains information such as the source and destination IP addresses, the protocol used, and the Time To Live (TTL) value. The TTL value is used to limit the number of routers that a packet can pass through before it is discarded.

The payload contains the data being transmitted, which can include TCP, UDP, or ICMP packets, among others.


IPv4 is a widely used protocol for addressing and routing data packets across a network. It provides a simple and efficient means of addressing and routing network traffic, although it is limited by its 32-bit addressing scheme. Despite its limitations, IPv4 remains an essential component of the internet and is likely to continue to be used for many years to come.

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