Network Identifiers

A typical device that is connected to a network has the following properties:

  • MAC Address

  • IP Address

  • Subnet Mask

  • Network Address

  • Broadcast Address

Example of a typical device network information:

Physical Address. . . . . . . . . : DC-41-A9-4A-EE-03
IPv4 Address. . . . . . . . . . . : 10.20.184.12
Subnet Mask . . . . . . . . . . . : 255.255.252.0
Network Address . . . . . . . . . : 10.20.184.0
Broadcast Address . . . . . . . . : 10.20.187.255
Default Gateway . . . . . . . . . : 10.20.184.1

MAC Address

Media Access Control (MAC) address (also known as physical address) is a unique identifier assigned to a device as a network address in communications within a network segment. MAC Address acts as the 'device ID' within a network. MAC Address work in OSI Layer 2 - Data Link.

MAC addresses are primarily assigned by device manufacturers in hardware, such as the card's read-only memory, or by a firmware mechanism. Many network interfaces, however, support changing their MAC address.

Currently, there are 2 formats of MAC Address: EUI-48 and EUI-64. Both are composed of pairs of Hexadecimals, seperated by dash -, semicolon :, or dot ., or not separated at all.

EUI-48 has 6 pairs of Hexadecimals, while EUI-64 has 8 pairs.

Example of EUI-48 MAC address:

  • 00-10-FA-6E-38-4A

  • 00:10:FA:6E:38:4A

  • 0010.FA6E.384A

  • 0010FA6E384A

Example of EUI-64 MAC address:

  • 2F-A2-09-5E-FF-83-B2-34

  • 2F:A2:09:5E:FF:83:B2:34

  • 2FA2.095E.FF83.B234

  • 2FA2095EFF83B234

IP Address

Internet Protocol (IP) address is a numerical label assigned to a device as a network address in communications between network segments. IP Address acts as the 'device location' between networks. IP Address work in OSI Layer 3 - Network.

IP addresses can be manually assigned, or automatically assigned by a DHCP Server.

Currently, there are 2 formats of IP Address: IPv4 and IPv6.

IPv4 addresses has a size of 32-bits, and are divided into 4 octets, each ranging between 0 - 255, separated by dot ..

IPv6 addresses has a size of 128-bits, and are divided into 8 octets, each comprised of 2 pairs of Hexadecimal characters, separated by semicolon :.

Example of IPv4 address:

  • 192.168.233.134

  • 172.168.15.23

  • 36.26.17.231

  • 8.0.0.8

Example of IPv6 address:

  • EF5A:11A9:2499:53E2:04B5:7713:2494:9EBD

  • F342:3A0D:9563:FEEB:2604:F0E2:E77E:C64D

  • 5780:BDF0:41BC:3293:6204:8E31:3F6A:4CDF

  • FED8:D7A7:E193:AAEA:6A11:2147:F835:C9EC

Subnet Mask

Subnet mask is a 32-bit number correlated with a host's network.

Subnet mask can be used to:

  • find the amount of endpoints a network can support.

  • find the network and broadcast address (using wildcard) from an IPv4 address.

Subnet mask is created by setting host bits to all 0 and setting network bits to all 1.

Subnet mask can be represented using a 4-octet system (just like IPv4 addresses), or using CIDR Notation, which counts the number of 1 s within the subnet mask, lead by slash /.

Example of subnet mask:

  • 255.255.255.0 /24

  • 255.255.0.0 /16

  • 255.255.252.0 /22

  • 255.0.0.0 /8

Note

Wildcard is the reverse of a subnet mask. It can be used to find the Broadcast Address of a network.

Network Address

Network Address is the address of the network a host resides.

Network Address can be calculated from the AND operation between a host's IPv4 address and its subsequent subnet mask.

For Example, to find the network address of an IPv4 Address 10.20.184.12/22 with the subnet /22 or 255.255.252.0:

  1. Convert the IP Address and the subnet mask into bits

 10. 20.184.12 = 00001010.00010100.10111000.00001100
255.255.252. 0 = 11111111.11111111.11111100.00000000

  1. Do an AND operation, and convert the result back into IPv4 address

 10. 20.184.12 = 00001010.00010100.10111000.00001100
255.255.252. 0 = 11111111.11111111.11111100.00000000
----------------------------------------------------&
                 00001010.00010100.10111000.00000000 = 10.20.184.0

The Network address of 10. 20.184.12/22 is 10.20.184.0.

Broadcast Address

Broadcast Address is the address used to broadcast message within a network.

Broadcast Address can be calculated from the OR operation between a host's IPv4 address and its subsequent wildcard.

For Example, to find the broadcast address of an IPv4 Address 10.20.184.12/22 with the subnet /22 or 255.255.252.0:

  1. Find the Wildcard of the subnet mask:

subnet   255.255.252.  0 = 11111111.11111111.11111100.00000000
wildcard   0.  0.  3.255 = 00000000.00000000.00000011.11111111

  1. Do an OR operation, and convert the result back into IPv4 Address

10. 20.184. 12 = 00001010.00010100.10111000.00001100
 0.  0.  3.255 = 00000000.00000000.00000011.11111111
----------------------------------------------------|
                 00001010.00010100.10111011.11111111 = 10.20.187.255

The Broadcast address of 10. 20.184.12/22 is 10.20.187.255.

Gateway Address

Gateway acts as the access point for the network.

When a packet wants to enter / exit the network, it has to go through the Gateway.

In most cases, the Gateway Address is the first address of the network, although this is completely configurable.

Note

If you are having a hard understanding these concepts, try the Apartment Terminology;

Imagine an apartment filled with rooms.

  • Network Address is the address of the actual apartment.

  • Broadcast Address is the announcement room, used to broadcast announcement to all of the tenants. It is always on the top floor.

  • Gateway Address is the lobby / receptionist of the apartment. It is usually on the first floor, although it can be on any floor.

  • Host IPv4 Address is the rooms of the tenants within the apartment.

  • MAC Address is your actual ID number. Your room may change, but you can never change your own ID.