MAC, IP and Gateway address

I was thinking of writing all about it by myself but this answer on Quora was so well written and knowledgeable that I thought of pasting it instead. This is the answer by anonymous:


MAC Address

A MAC address is a 6-byte hexadecimal address that allows a NIC to be uniquely identified on the network. The MAC address forms the basis of network communication, regardless of the protocol used to achieve network connection.A Media Access Control address (MAC address) is a  unique identifier assigned to a network interface card (NIC) by its  manufacturer. The network interface card is used to connect to the  Ethernet network. Each NIC has its own unique MAC address. The MAC  addresses are assigned permanently to adapters and cannot be changed as  they are a unique identification of the hardware interface of network.

The MAC addresses are stored in the NIC’s hardware, its read-only  memory, or some other firmware mechanism. The address encodes the  manufacturer’s registered identification number. A MAC address can also  be referred to as the burned-in address, Ethernet hardware address  (EHA), hardware address or physical address.

Packets that are sent on the ethernet are always coming from a MAC  address and sent to a MAC address. If a network adapter is receiving a  packet, it is comparing the packet’s destination MAC address to the  adapter’s own MAC address. If the addresses match, the packet is  processed, otherwise it is discarded.

The MAC addresses are formed and assigned according to the rules of one  of three numbering name spaces managed by the Institute of Electrical  and Electronics Engineers (IEEE): MAC-48, EUI-48, and EUI-64. The first  half of the MAC address tells what brand/model the card is, and the  second half is a unique identifier specific to that card.

For example, consider the MAC address of the computer on which this book is being written: 00:D0:59:09:07:51. The first three bytes (00:D0:59) identify the manufacturer of the card; because only this manufacturer can use this address, it is known as the Organizational Unique Identifier(OUI). The last three bytes (09:07:51) are then referred to as the Universal LAN MAC address: They make this interface unique.

How to find the MAC address of your computer(any version of Windows):-

  1. Open the command prompt. Press the Win+R keys and type cmd into the Run field. Press Enter(↵) to start the Command Prompt.
  2. Run GetMAC. At the command prompt, type getmac /v /fo list and press Enter(↵). This will display configuration information for all of your network connections.
  3. Look for the physical address which would be your MAC address


IP address
In order to transfer data from one location to another, it must first  know where the users are located. IP distinguishes these as IP  addresses. The IP address is a number that is assigned to each device,  such as a computer, a printer, etc. It describes where on the Internet  your computer is located. An IP address is required by any device that  participates in a computer network that uses the Internet Protocol for  communication.

There are two standards for IP addresses: IP Version 4 (IPv4) and IP  Version 6 (IPv6). All computers with IP addresses have an IPv4 address,  and many are starting to use the new IPv6 address system as well. Here’s  what these two address types mean:

  • IPv4 uses 32 binary bits  to create a single unique address on the network. An IPv4 address is  expressed by four numbers separated by dots. Each number is the decimal  (base-10) representation for an eight-digit binary (base-2) number, also  called an octet. For example: 216.27.61.137
  • IPv6 uses 128  binary bits to create a single unique address on the network. An IPv6  address is expressed by eight groups of hexadecimal (base-16) numbers  separated by colons, as in 2001:cdba:0000:0000:0000:0000:3257:9652.  Groups of numbers that contain all zeros are often omitted to save  space, leaving a colon separator to mark the gap (as in  2001:cdba::3257:9652).

How does your computer get its IP address? An IP address can be either  dynamic or static. A static address is one that you configure yourself  by editing your computer’s network settings. This type of address is  rare, and it can create network issues if you use it without a good  understanding of TCP/IP. Dynamic addresses are the most common. They’re  assigned by the Dynamic Host Configuration Protocol (DHCP), a service  running on the network. DHCP typically runs on network hardware such as routers or dedicated DHCP servers.

IP Classes
  • 0.0.0.0 — This represents the default network, which is the abstract concept of just being connected to a TCP/IP network.
  • 255.255.255.255 — This address is reserved for network broadcasts, or messages that should go to all computers on the network.
  • 127.0.0.1 — This is called the loopback address, meaning your computer’s way of  identifying itself, whether or not it has an assigned IP address.
  • 169.254.0.1 to 169.254.255.254 — This is the Automatic Private IP Addressing (APIPA) range of  addresses assigned automatically when a computer’s unsuccessful getting  an address from a DHCP server.

The other IP address  reservations are for subnet classes. A subnet is a smaller network of  computers connected to a larger network through a router. The subnet can  have its own address system so computers on the same subnet can  communicate quickly without sending data across the larger network. A  router on a TCP/IP network, including the Internet, is configured to  recognize one or more subnets and route network traffic appropriately.


The following are the IP addresses reserved for subnets:

10.0.0.0 to 10.255.255.255 — This falls within the Class A address range of 1.0.0.0 to 127.0.0.0, in which the first bit is 0.

  • 172.16.0.0  to 172.31.255.255 — This falls within the Class B address range of  128.0.0.0 to 191.255.0.0, in which the first two bits are 10.
  • 192.168.0.0  to 192.168.255.255 — This falls within the Class C range of 192.0.0.0  through 223.255.255.0, in which the first three bits are 110.
  • Multi-cast  (formerly called Class D) — The first four bits in the address are  1110, with addresses ranging from 224.0.0.0 to 239.255.255.255.
  • Reserved for future/experimental use (formerly called Class E) — addresses 240.0.0.0 to 254.255.255.254.

Check this link to find the IP address:- How to Find the IP Address of Your PC


Gateway address
The gateway address (or default gateway) is a router interface connected to the local network that sends packets out of the local network. The gateway has a physical and a logical address.

Logical Gateway Address

The gateway operates at the network layer (Layer 3) of the OSI Model. The gateway is used when transmitting packets. When packets are sent over a network, the destination IP address is examined. If the destination IP is outside of the network, then the  packet goes to the gateway for transmission outside of the network. The  gateway is on the same network as end devices. The gateway address must  have the same subnet mask as host devices. Each host on the network uses the same gateway.
The gateway should have a static address, as changing the address  would cause packets not to be delivered. The gateway is typically  assigned either the highest or lowest network address. This is not a  requirement, but many organizations use a consistent addressing scheme  to facilitate network planning.

Physical Gateway Address

The gateway also operates at the data link layer (Layer 2) of the OSI network model. The physical gateway address is called the media access control(MAC) address or burned in address (BIA). The physical address is assigned when the device is manufactured, and cannot be changed. When a frame is sent to a device not on the local network, the gateway’s MAC address is used in the frame header.

You will need your default gateway to allow you to access your admin settings on your router.

After you find out what your default gateway is, you will  be able to make changes to your routers settings. You will use the  default gateway address to access your admin settings of your router. To  do this, type the default gateway address into the address bar of your  browser and hit enter. You will then be prompted for a username and  password. This information can sometimes be found on your router or  direction pamphlet. If you can’t find it on either, you can search the  internet by typing your routers make and model and “default  administrator password”. This will only work if you have not changed the  password on your router. If you have changed the default password and  forget it, you will need to reset your router.
http://10.1.1.1  or  http://192.168.1.1 are both examples of default gateways.


How to find your Gateway address(for Windows users):-

1) Open the command prompt:- Press the Win+R keys and type cmd into the Run field. Press to start the Command Prompt.

2) Type “ipconfig”:- Next type ‘ipconfig’ and press enter Enter(↵) .

3)Look for the “default gateway” which would be the gateway address you are looking for.