Network_IP

Functions of Layer 3

1. Although computers use MAC addresses to communicate with each other,

    for the convenience of people, they use IP addresses to send and receive data.

 

2. It serves the role of connecting LANs (Local Area Networks).

 

3. The device used to connect LANs is a router (OSI Layer 3).

 

 

IP Address

1. IPv4 address: The IP address currently assigned to the PC.

 

2. Subnet mask: Defines the range of the network for an IP address.

 

3. Gateway address: The network's gateway used for communication with external networks.

 

4. An IP address is formatted as xxx.xxx.xxx.xxx, divided into four fields.

   The range of numbers in each field is from 0 to 255.

 

 

Layer 3 Protocols

1. ARP Protocol: Used to obtain MAC addresses using IP addresses.

 

2. IPv4 Protocol: Used for communication on WAN (Wide Area Network).

 

3. ICMP Protocol: Used to check if communication is successful between devices.

 

 

Private IP and Public IP

1. When devices using private IP addresses connect to an external environment,

    their addresses are changed to public IPs.

 

2. The process of converting a public IP to a private IP is called

    Network Address Translation (NAT).

Example: If you search for your IP on Naver website from computers in the same classroom,

                 the result will be the same for all computers. This is the public IP.

  

                However, if you check the IP through the command prompt (cmd) on

                each individual computer, you'll see different IPs. This is the private IP.

 

 

 

Special IP Addresses

• 0.0.0.0: Refers to all other IPs.
• 127.0.0.1: Represents the address of the device itself (localhost).