IPv4 CIDR Address Calculator

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Private IPv4 Addresses

Private IPv4 addresses are reserved for use within private networks and are not routable on the public internet. These addresses are commonly used in home and corporate networks. The following table lists the ranges of private IPv4 addresses as defined by RFC 1918.

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Common Private IPv4 CIDR Ranges

An IPv4 CIDR Range is a way to specify a range of IP addresses using CIDR notation. CIDR notation is a compact representation of an IP address and its associated network mask. It is used to specify the number of bits in the subnet mask, which determines how many addresses are available in the range.

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Acceptable CIDR Values

The following CIDR values are acceptable for IPv4 addresses:

CIDR Value	Subnet Mask	Number of Hosts
/0	255.0.0.0	4,294,967,296
/1	255.0.0.0	2,147,483,648
/2	255.0.0.0	1,073,741,824
/3	255.0.0.0	536,870,912
/4	255.0.0.0	268,435,456
/5	255.0.0.0	134,217,728
/6	255.0.0.0	67,108,864
/7	255.0.0.0	33,554,432
/8	255.255.0.0	16,777,216
/9	255.255.0.0	8,388,608
/10	255.255.0.0	4,194,304
/11	255.255.0.0	2,097,152
/12	255.255.0.0	1,048,576
/13	255.255.0.0	524,288
/14	255.255.0.0	262,144
/15	255.255.0.0	131,072
/16	255.255.255.0	65,536
/17	255.255.255.0	32,768
/18	255.255.255.0	16,384
/19	255.255.255.0	8,192
/20	255.255.255.0	4,096
/21	255.255.255.0	2,048
/22	255.255.255.0	1,024
/23	255.255.255.0	512
/24	255.255.255.255	256
/25	255.255.255.255	128
/26	255.255.255.255	64
/27	255.255.255.255	32
/28	255.255.255.255	16
/29	255.255.255.255	8
/30	255.255.255.255	4
/31	255.255.255.255	2
/32	255.255.255.255	1

Note: The number of hosts is calculated as 2^(32 - CIDR).

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Fun IPv4 Facts

• IPv4 is a fundamental part of the internet and is used by billions of devices every day. Understanding IPv4 is essential for anyone working in networking, system administration, or IT.
• IPv4 is a 32-bit address space, which means it can support 2^32 addresses. This is approximately 4.3 billion addresses.
• IPv4 addresses are typically written in decimal as four numbers separated by periods. Each number can be between 0 and 255.
• IPv4 addresses are divided into five classes: A, B, C, D, and E. Classes A, B, and C are used for unicast addressing, while class D is used for multicast addressing and class E is reserved for future use.
• IPv4 addresses are also divided into public and private addresses. Public addresses are routable on the internet, while private addresses are not. Private addresses are used for local networks and are not routable on the internet.
• IPv4 addresses are typically assigned using DHCP (Dynamic Host Configuration Protocol), which allows devices to automatically obtain an IP address from a DHCP server.
• IPv4 addresses can also be assigned statically, which means that the address is manually configured on the device.
• IPv4 addresses can be represented in different formats, including dotted-decimal notation, hexadecimal notation, and binary notation.
• IPv4 addresses can be subnetted, which means that a single IP address can be divided into multiple smaller networks. This is done by using a subnet mask, which specifies the number of bits used for the network portion of the address.
• IPv4 addresses can also be represented in CIDR (Classless Inter-Domain Routing) notation, which allows for more flexible subnetting.
• IPv4 addresses are running out, which is why IPv6 was developed. IPv6 uses a 128-bit address space, which can support 2^128 addresses. This is an astronomical number of addresses and should be sufficient for the foreseeable future.
• IPv4 addresses can be converted to IPv6 addresses using a process called IPv4-mapped IPv6 addresses. This allows IPv4 addresses to be represented in an IPv6 format, which can be useful for compatibility with IPv6 networks.
• IPv4 addresses can also be represented in a compressed format, which reduces the number of bits used to represent the address. This is done by removing leading zeros and using "::" to represent consecutive groups of zeros.
• IPv4 addresses can be used in conjunction with NAT (Network Address Translation), which allows multiple devices on a local network to share a single public IP address. This is commonly used in home networks and small businesses.
• IPv4 addresses can also be used in conjunction with VPN (Virtual Private Network) technology, which allows secure communication over the internet. This is commonly used for remote access to corporate networks and for secure communication between devices on different networks.
• IPv4 addresses can also be used in conjunction with firewalls, which can be used to control access to networks and devices. Firewalls can be configured to allow or block traffic based on IP addresses, ports, and protocols.
• IPv4 addresses can also be used in conjunction with load balancers, which can distribute traffic across multiple servers. This is commonly used for high-availability and scalability in web applications.
• IPv4 addresses can also be used in conjunction with DNS (Domain Name System), which translates domain names into IP addresses. This allows users to access websites using human-readable names instead of IP addresses.
• IPv4 addresses can also be used in conjunction with DHCP reservations, which allow specific devices to always receive the same IP address from a DHCP server. This is commonly used for printers and other devices that need a static IP address.
• IPv4 addresses can also be used in conjunction with ARP (Address Resolution Protocol), which is used to map IP addresses to MAC addresses. This is commonly used in local networks to allow devices to communicate with each other.
• IPv4 addresses can also be used in conjunction with ICMP (Internet Control Message Protocol), which is used for error reporting and diagnostics. This is commonly used for pinging devices and for network troubleshooting.
• IPv4 addresses can also be used in conjunction with SNMP (Simple Network Management Protocol), which is used for network monitoring and management. This is commonly used for monitoring network devices and for collecting performance data.
• IPv4 addresses can also be used in conjunction with RARP (Reverse Address Resolution Protocol), which is used to map MAC addresses to IP addresses. This is commonly used for diskless workstations and other devices that need to obtain an IP address from a server.
• IPv4 addresses can also be used in conjunction with DHCP relay agents, which allow DHCP requests to be forwarded between different networks. This is commonly used in large networks with multiple subnets.
• IPv4 addresses can also be used in conjunction with IPsec (Internet Protocol Security), which is used for secure communication over the internet. This is commonly used for VPNs and for securing communication between devices on different networks.
• IPv4 addresses can also be used in conjunction with GRE (Generic Routing Encapsulation), which is used for tunneling protocols. This is commonly used for VPNs and for encapsulating other protocols over IP networks.
• IPv4 addresses can also be used in conjunction with MPLS (Multiprotocol Label Switching), which is used for traffic engineering and for improving the performance of IP networks. This is commonly used in service provider networks and for large enterprise networks.
• IPv4 addresses can also be used in conjunction with BGP (Border Gateway Protocol), which is used for routing between different autonomous systems. This is commonly used in service provider networks and for interconnecting different networks.
• IPv4 addresses can also be used in conjunction with OSPF (Open Shortest Path First), which is used for routing within a single autonomous system. This is commonly used in enterprise networks and for interconnecting different networks.
• IPv4 addresses can also be used in conjunction with EIGRP (Enhanced Interior Gateway Routing Protocol), which is used for routing within a single autonomous system. This is commonly used in enterprise networks and for interconnecting different networks.
• IPv4 addresses can also be used in conjunction with RIP (Routing Information Protocol), which is used for routing within a single autonomous system. This is commonly used in small networks and for interconnecting different networks.

For more information on IPv4, check out the Wikipedia page.