MAC Addresses

Sat, 16 Jul 2022 11:30:00 +0530

What is a MAC Address?

A media access control (MAC) address is a unique identification number assigned to every network interface controller (NIC).

MAC addresses are assigned by the device manufacturer and are burned-in to the NIC.

MAC Addresses are also called

Burned-in address: as the address is burned into the Read-only Memory (ROM) of the NIC,
Physical address: The MAC address is the unique hardware address of every NIC,
Hardware address
Ethernet hardware address

Structure of MAC Address

A MAC address is a 48-bit address. It has 6 groups of 2 hexadecimal digits.

The 6 octets are separated by colons (:), hyphens (-), or left without a separator.

Organizationally Unique Identifier

The first 3 octets of a MAC address represent the manufacturer of the NIC.

The OUI are assigned by the IEEE Registration Authority.

For example,

OUI	Organization
AC:ED:5C	Intel Corporate
CC:46:D6	Cisco Systems, Inc
F8:8F:CA	Google, Inc.
C4:2A:D0	Apple, Inc.

Manufacturers usually have multiple OUIs. The full list of OUIs is here.

Some virtualisation softwares have their own OUIs, such as VMware (00:50:56), QEMU (52:54:00), etc.

Network Interface Controller

The NIC is the hardware component that connects a device to the network, such an adapter or card.

The last 3 octets of the MAC address identify the NIC.

IP Addresses

Thu, 30 Jun 2022 20:00:00 +0530

Internet Protocol

The Internet Protocol (IP) is the protocol by which data is sent across the Internet.

What is an IP address?

An IP address is a unique string of numbers assigned to every device connected to the Internet.

Types of IP addresses

Dynamic IP

Dynamic IP addresses are temporary addresses that change from time to time.

They are assigned to devices on a network by the Dynamic Host Configuration Protocol (DHCP).

Static IP

Static IP addresses are permanent addresses that do not change until the device is decommissioned.

Public IP

Public (or) external IP addresses can be accessed directly over the Internet and are used for external communications.

Public IP addresses are assigned to a router or network by the Internet Service Provider (ISP).

Private IP

Private (or) internal (or) local IP addresses are assigned to all devices connected to a network. They are the same for any network.

Ranges:

Class A: 10.0.0.0 to 10.255.255.255
Class B: 172.16.0.0 to 172.31.255.255
Class C: 192.168.0.0 to 192.168.255.255

Note: These are IPv4 addresses (more on that later)

Shared IP

A shared IP address is used by multiple domains or websites.

Dedicated IP

A dedicated IP address is an address allotted exclusively to one website.

Loopback IP

Data sent to a loopback address are looped and sent back to the device.

They are managed entirely within the operating system (the data never reaches the network).

Range: 127.0.0.0 to 127.255.255.255 (IPv4)

The most common loopback address is localhost (IPv4: 127.0.0.1, IPv6: ::1).

Versions of IP

Currently, there are two version of IP publicly used - IPv4 and IPv6.

IPv4

Internet Protocol version 4 (IPv4) is the first public version of the IP.

IPv4 is a 32-bit address. It has 4 octets.

In November 2019, we ran out of unallocated IPv4 addresses. However, IPv4 addresses continue to be in use and will most likely coexist with IPv6 for many years.

IPv6

Internet Protocol version 6 (IPv6) is the second public version of the IP, intended to become a successor to IPv4.

IPv6 is a 128-bit address. It has 16 octets. Each octet ranges from 0000 to FFFF (hexadecimal values).

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