Introduction
IPv4, or Internet Protocol version 4, is a widely used network protocol that defines how devices in a computer network communicate with each other over the internet. It is one of the core protocols that form the foundation of the internet. IPv4 addresses are numerical labels assigned to devices participating in a network to identify and locate them.
Private & Public Addresses
Public IP addresses are globally unique and can be used to communicate directly with other devices on the internet. They are assigned by Internet Service Providers (ISPs) to devices that need to communicate with other devices on the internet, such as servers, routers, or computers. Public IP addresses are not part of the private IP address ranges, which are reserved for use on private networks and cannot be directly routed on the internet.
Private Addresses
Private IP addresses are reserved for use in private networks. They are not routable on the public internet and are used for communication within a private network only. Private IP addresses are commonly used in home and small office networks, as well as in larger corporate networks. Devices on a private network can communicate with each other using these addresses without the need for public IP addresses or access to the internet. One advantage of using private IP addresses is that they can be reused within multiple private networks, since they are not globally unique. This allows for greater flexibility and scalability in network design. However, private IP addresses cannot be used for public-facing servers or services, as they are not reachable from the public internet. To enable access to public-facing services, network address translation (NAT) is commonly used to translate private IP addresses to public IP addresses when communicating with the internet.
Public Addresses
Public IP addresses are assigned to devices that are connected to the public internet. They are globally unique and can be accessed from anywhere in the world. Public IP addresses are typically assigned to devices such as web servers, email servers, and other servers that need to be accessible from the internet. They are also assigned to devices such as routers and modems that provide access to the internet for other devices on a network. Public IP addresses are allocated by Internet Assigned Numbers Authority (IANA) to regional Internet registries (RIRs), which in turn allocate them to internet service providers (ISPs) and other organizations. ISPs then assign public IP addresses to their customers. One key characteristic of public IP addresses is that they are publicly visible on the internet. This means that devices with public IP addresses can be reached from anywhere on the internet. However, this also makes them vulnerable to attacks from malicious actors, which is why it's important to implement proper security measures, such as firewalls and intrusion detection systems, to protect devices with public IP addresses. Public IP addresses can be either static or dynamic. Static IP addresses remain the same over time and are typically used for devices that need to be accessed consistently, such as servers. Dynamic IP addresses, on the other hand, are assigned by ISPs using Dynamic Host Configuration Protocol (DHCP) and can change periodically. They are typically used for devices that do not require a consistent IP address, such as personal computers and mobile devices.
Localhost
The localhost IP address range refers to a range of IP addresses that are reserved for loopback interfaces on devices. These addresses are used to refer to the device itself and are not used for communication with other devices on a network. The most commonly used localhost IP address is 127.0.0.1, which is a part of the localhost IP address range. This range includes all IP addresses in the block 127.0.0.0/8, which means any IP address that begins with 127 is a localhost address. The 127.0.0.0/8 range includes 16,777,214 unique IP addresses, ranging from 127.0.0.0 to 127.255.255.255. However, only the address 127.0.0.1 is commonly used as the loopback address. The use of the localhost IP address range is important for testing and development purposes, as it allows developers to test services and applications without exposing them to the public internet. It is also used for troubleshooting and diagnostic purposes, as it allows you to test network connectivity and service availability on the device itself.
Multicast
Multicast IP addresses are used for one-to-many communication, where data packets are sent from one sender to multiple receivers. Multicast addresses are defined within the IPv4 and IPv6 address spaces. In IPv4, multicast addresses are defined within the range of 224.0.0.0 to 239.255.255.255. The range from 224.0.0.0 to 224.0.0.255 is reserved for local network control purposes, such as multicast routing protocols like OSPF. Addresses from 224.0.1.0 to 238.255.255.255 are globally routable and can be used for general multicast communication within networks. The remaining range, from 239.0.0.0 to 239.255.255.255, is reserved for administratively scoped multicast addresses, which are typically used within private networks or domains.
IPv4 Subnetting Table
An IPv4 subnetting table is a tool used to organize and manage IP address allocation within a network. It provides a structured way to visualize how IP addresses are divided into smaller subnetworks, each with its own range of addresses. Subnetting allows network administrators to efficiently allocate IP addresses, optimize network performance, and manage network resources effectively.
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