A definition of IPv4

Internet Protocol version 4 (IPv4) is the fourth edition of the Internet Protocol. It is a system of identifying individual computers and digital devices on the Internet by assigning each one with a unique address.

IPv4 address consists of a set of four numbers separated by a period character (“.”), often referred to as a “dot.” Each number can be from 0 to 254. Some addresses may not be assigned because they are reserved for special uses. IPv4 can accommodate up to 4 billion unique addresses, but these have already been used up as the Internet continues to grow.

You can think of IPv4 as the unique ID which a computer, smartphone, or game console displays to communicate with similar devices.


In the IPv4 IP address space, there are five classes: A, B, C, D and E. Each class has a specific range of IP addresses (and ultimately dictates the number of devices you can have on your network). Primarily, class A, B, and C are used by the majority of devices on the Internet. Class D and class E are for special uses.

The list below shows the five available IP classes, along with the number of networks each can support and the maximum number of hosts (devices) that can be on each of those networks. The four octets that make up an IP address are conventionally represented by a.b.c.d – such as

Additionally, information is also provided on private addresses and loop address (used for network troubleshooting).

Class A Public Address

Class A addresses are for networks with large number of total hosts. Class A allows for 126 networks by using the first octet for the network ID. The first bit in this octet, is always set and fixed to zero. And next seven bits in the octet is all set to one, which then complete network ID. The 24 bits in the remaining octets represent the hosts ID, allowing 126 networks and approximately 17 million hosts per network. Class A network number values begin at 1 and end at 127.

  • IP Range: to
    • First octet value range from 1 to 127
  • Subnet Mask: (8 bits)
  • Number of Networks: 126
  • Number of Hosts per Network: 16,777,214

Class B Public Address

Class B addresses are for medium to large sized networks. Class B allows for 16,384 networks by using the first two octets for the network ID. The two bits in the first octet are always set and fixed to 1 0. The remaining 6 bits, together with the next octet, complete network ID. The 16 bits in the third and fourth octet represent host ID, allowing for approximately 65,000 hosts per network. Class B network number values begin at 128 and end at 191.

  • Range: to
    • First octet value range from 128 to 191
  • Subnet Mask: (16 bits)
  • Number of Networks: 16,382
  • Number of Hosts per Network: 65,534

Class C Public Address

Class C addresses are used in small local area networks (LANs). Class C allows for approximately 2 million networks by using the first three octets for the network ID. In class C address three bits are always set and fixed to 1 1 0. And in the first three octets 21 bits complete the total network ID. The 8 bits of the last octet represent the host ID allowing for 254 hosts per one network. Class C network number values begin at 192 and end at 223.

  • Range: to
    • First octet value range from 192 to 223
  • Subnet Mask: (24 bits)
  • Number of Networks: 2,097,150
  • Number of Hosts per Network: 254

Class D Address Class

Classes D are not allocated to hosts and are used for multicasting.

  • Range: to
    • First octet value range from 224 to 239
  • Number of Networks: N/A
  • Number of Hosts per Network: Multicasting

Class E Address Class

Classes E are not allocated to hosts and are not available for general use. They are reserved for reseach purposes.

  • Range: to
    • First octet value range from 240 to 255
  • Number of Networks: N/A
  • Number of Hosts per Network: Research/Reserved/Experimental

Private Addresses

Within each network class, there are designated IP address that is reserved specifically for private/internal use only. This IP address cannot be used on Internet-facing devices as that are non-routable. For example, web servers and FTP servers must use non-private IP addresses. However, within your own home or business network, private IP addresses are assigned to your devices (such as workstations, printers, and file servers).

  • Class A Private Range: to
  • Class B Private APIPA Range: to
    • Automatic Private IP Addressing (APIPA) is a feature on Microsoft Windows-based computers to automatically assign itself an IP address within this range if a Dynamic Host Configuration Protocol (DHCP) server is not available. A DHCP server is a device on a network that is responsible for assigning IP address to devices on the network.
  • Class B Private Range: to
  • Class C Private Range: to

Special Addresses

  • IP Range: to are network testing addresses (also referred to as loop-back addresses)

Features of IPv4

  • Connectionless Protocol.
  • Allow creating a simple virtual communication layer over diversified devices.
  • It requires less memory, and ease of remembering addresses.
  • Already supported protocol by millions of devices.
  • Offers video libraries and conferences.

How Ipv4 works

IPv4 works on the network layer of the TCP/IP protocol stack. The main task of the protocol is to transfer data blocks from the sending host to the destination host, where the senders and receivers are computers that are uniquely identified by IP addresses

How is IPv6 different?

Internet Protocol Version 6 or IPv6 is the newest version of Internet Protocol used for carrying data in packets from one source to a destination via various networks. IPv6 is considered as an enhanced version of the older IPv4 protocol, as it supports a significantly larger number of nodes than the latter.

IPv6 allows up to 2128 possible combinations of nodes or addresses. It is also referred to as the Internet Protocol Next Generation or IPng. It was first developed in the hexadecimal format, containing eight octets to provide more substantial scalability. Released on June 6, 2012, it was also designed to deal with address broadcasting without including broadcast addresses in any class, the same as its predecessor.

comparing difference between ipv4 and ipv6

Comparing Difference Between IPv4 and IPv6

Now that you know more about IPv4 and IPv6 in detail, we can summarize the differences between these two protocols in a table. Each has its deficits and benefits to offer.

Points of DifferenceIPV4IPV6
Compatibility with Mobile DevicesAddresses use of dot-decimal notations, which make it less suitable for mobile networks.Addresses use hexadecimal colon-separated notations, which make it better suited to handle mobile networks.
MappingAddress Resolution Protocol is used to map to MAC addresses.Neighbor Discovery Protocol is used to map to MAC Address.
Dynamic Host Configuration ServerWhen connecting to a network, clients are required to approach Dynamic Host Configuration Servers.Clients are given permanent addresses and are not required to contact any particular server.
Internet Protocol SecurityIt is optional.It is mandatory.
Optional FieldsPresentAbsent. Extension headers are available instead.
Local Subnet Group ManagementUses Internet Group Management Protocol or GMP.Uses Multicast Listener Discovery or MLD.
IP to MAC resolutionFor Broadcasting ARP.For Multicast Neighbor Solicitation.
Address ConfigurationIt is done manually or via DHCP.It uses stateless address autoconfiguration using the Internet Control Message Protocol or DHCP6.
DNS RecordsRecords are in Address (A).Records are in Address (AAAA).
Packet HeaderPacket flow for QoS handling is not identified. This includes checksum options.Flow Label Fields specify packet flow for QoS handling.
Packet FragmentationPacket Fragmentation is allowed from routers when sending to hosts.For sending to hosts only.
Packet SizeThe minimum packet size is 576 bytes.Minimum packet size 1208 bytes.
SecurityIt depends mostly on Applications.Has its own Security protocol called IPSec.
Mobility and InteroperabilityNetwork topologies are relatively constrained, which restricts mobility and interoperability.IPv6 provides mobility and interoperability capabilities which are embedded in network devices
SNMPSupport included.Not supported.
Address MaskIt is used for the designated network from the host portion.Not Used
Address FeaturesNetwork Address Translation is used, which allows a single NAT address to mask thousands of non-routable addresses.Direct Addressing is possible because of the vast address space.
Configuration the NetworkNetworks are configured either manually or with DHCP.It has autoconfiguration capabilities.
Routing Information ProtocolSupports RIP routing protocol.IPv6 does not support RIP routing protocol.
FragmentationIt’s done by forwarding and sending routes.It is done only by the sender.
Virtual Length Subnet Mask SupportSupports added.Support not added.
ConfigurationTo communicate with other systems, a newly installed system must be configured first.Configuration is optional.
Number of ClassesFive Different Classes, from A to E.It allows an unlimited number of IP Addresses to be stored.
Type of AddressesMulticast, Broadcast, and UnicastAnycast, Unicast, and Multicast
Checksum FieldsHas checksum fields, example: present
Length of Header Filed2040
Number of Header fields128
Address MethodIt is a numeric address.It is an alphanumeric address.

Benefits of IPv4

  • Simple Topology Drawings: IPv4 protocols have simple prefixes. This essentially means that they can easily fit on all your topology drawings when you decide to opt for IPv4. …
  • System Support: The best thing about IPv4 protocols is that all systems have no problem handling IPv4 routing.

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