Networking Intro

Internet

• The internet is a public network that anyone can access.

• Internet is a global network of computers that allows anyone to access it.

Intranet

• An intranet is a private network that only users within an organization can access.

• An intranet is usually set up for a specific purpose, such as sharing information or files within an organization.

• It is not accessible to people outside the organization.

IP Address:

• The Internet Protocol Address (or IP Address) is a unique address that computing devices such as personal computers, tablets, and smartphones use to identify itself and communicate with other devices in the IP network.

Routing devices in AWS launch an instance and they will take IP address from the ISP pool.

Once you receive public ip address, that means it is injected into the Internet in 1:1 ratio.

If you create another Server, you will get another public Ip address in 1:1 ratio.

Users try to access your servers by using public Ip address.

Servers cannot be accessed directly because they are protected by Firewalls.

Firewalls

• Firewalls help in protecting servers from network traffic. In AWS, security group acts as Firewall.

• Firewall will stop traffic from unwanted source to server.

• Firewall is a security system that blocks or allows network traffic based on as set of security rules and it usually sits in between trusted and untrusted network (Internet).

Network is designed in such a way that every server is reserved with one port number. i.e., Service ports has 0–65535 port numbers.

Ports

• Ports allow communication between devices. Internet facing servers and applications essentially listen on ports for a connection from outside to do their jobs.

• Without ports, communication between hosts over the internet is not possible.

• Ports are software based & managed by Computer’s OS. each port is associated with a specific process or service.

Most commonly used Ports

• Port 20 & 21 →FTP is transforming files between client & Server.

• Port 25 → SMTP used for E-mail.

• Port 22 → Secure Shell (SSH)

• Port 53 →DNS

• Port 80 → HTTP

• Port 443 →HTTPs (Secure & Encrypted version of HTTP)

• Port 123 → NTP (Allows Compute Clocks to sync with each other)

• Port 179 →BGP (Border gateway Protocol)

• Port 500->ISAKMP (Internet Securely Association & Key Management Protocol)

• Port 587 →Modern, Secure SMTP that uses encryption.

• Port 3389 →RDP (Remote Desktop Protocol)

ip a → To identify the Ip address.

netstat -lntp \ → shows all the ports which are Active.

sudo netsat -lntp → Shows Network status and protocol statistics.

telnet ip-address-port→ Check whether port is open or not.

Difference between Public & Private Network

• Private Ip address is used to communicate within the same network. Using Private Ip data or information can be sent or received within the same network.

• Public Ip address is used to communicate outside the network. A public Ip address is basically assigned by the Internet Service Provider.