IPv4 Overview

IPv4 Overview

IPv4 Overview

The original version of IP, IPv4 is still very much in-use and alive across the globe. Addresses are 32 bits long, with groups of eight bits (octets) shown divided by a period. IPv4 address include "", "", "", and many more. The total range of IPv4 addresses is shown below: -

All IPv4 addresses in the world are somewhere within that range. Each subnet is a "slice" of the much larger address space.

  1. Public Addresses
  2. Private Addresses
  3. Loopback Addresses
  4. APIPA Addresses
  5. Multicast Addresses
  6. Broadcast Addresses
  7. Classful Addresses

Public Addresses

Most IPv4 addresses are publicly-routable, typical addresses. They can be used on devices like routers to send data across public networks like the internet. Putting a public address on an internet-facing resource like a web or mail server makes it available to users in other networks. Examples of public addresses include "", "", and "".

Most ISP subscribers have a single public address assigned on their router, and private addresses are used internally for LAN devices like printers and desktops.

Private Addresses

Special address blocks inside the full range have been set aside for internal use by RFC-1918. These blocks include the following:

Network Prefix Address Range Total Addresses
10/8 - 16,777,216
172.16/12 - 1,048,576
192.168/16 - 65,536

These addresses can be used in private networks like homes or businesses, and they don't have to be registered. Unfortunately, these private blocks aren't routable on the internet, so a mechanism like NAT must be used to translate connections from private to public addresses.

The use of private addresses slowed the exhaustion of IPv4 addresses, but it's reached the point where IPv6 adoption is becoming a requirement.

Loopback Addresses

The network is reserved for local or "Loopback" interfaces. Typically is assigned to the first network interface. Other addresses can be assigned to other loopback addresses as needed. The address block is routable, but most ISPs blackhole this range at the edge of their network.

APIPA Addresses

RFC-3927 defined the Automatic Private IP Addressing (APIPA) block for use as Link-Local addresses. The network is reserved for APIPA. DHCP clients that cannot get an address lease will automatically assign themselves an APIPA address. While using the APIPA address block for internal networking is possible, it is not recommended. Some organizations monitor networks for the presence of 169.254.X.X traffic, which means hosts are failing to auto-configure (DHCP, PXE-Boot, etc.)

Multicast Addresses

Multicast addresses are set aside for special multicast (one-to-many) traffic. Some of these addresses include the following:

Multicast Address Usage All Hosts All Routers All OSPF Routers OSPF DRs RIPv2 Routers EIGRP Routers PIMv2 VRRP Devices IS-IS Routers Multicast NTP

Broadcast Address

The address is set aside for broadcast traffic on the local network. Anything sent to this address is received by all hosts, but not routed from one network to another.

Classful Addresses

Early in the history of IPv4, address blocks were broken up into classes with different, static sizes. When IP addresses were assigned to organizations, they were in one class or another depending on how many hosts their network had. Routers and routing protocols only worked with addresses in these monolithic classes. The following classes were defined historically:

Class Address Range Block Size (host bits) Addresses Usage
Class A - 24 16,777,216 Large networks
Class B - 16 65,536 Medium networks
Class C - 8 256 Small networks
Class D - -- -- Multicast
Class E - -- -- Reserved

As IPv4 addresses were rapidly consumed with more companies and individuals coming online, large classful blocks could no longer be assigned. Classless assignment of IPv4 addresses is now standard across the globe, with subscribers only getting as many public IP addresses as they can provide justification for.

MikroTik Hyper-V Serial Console

MikroTik Hyper-V Serial Console

Wiping MikroTik Devices

Wiping MikroTik Devices