Lecture Notes: Key Port Numbers and Their Uses

Introduction

• Understanding TCP and UDP port numbers is crucial for:
  • Troubleshooting communication issues.
  • Configuring firewalls.
• Ports are criteria for allowing/blocking network traffic.
• Memorizing port numbers is essential for A+ studies.
• Importance of knowing protocols, their significance, and usage.

File Transfer Protocol (FTP)

• Ports: TCP Port 20 (active data transfer), TCP Port 21 (administration/control)
• Used for transferring files across different operating systems.
• Requires authentication (username/password) or can allow anonymous access.
• Allows file management functions: add, delete, rename, etc.

Secure Shell (SSH)

• Port: TCP Port 22
• Provides encrypted communication for secure command-line access.
• Preferred over Telnet due to encryption.

Telnet

• Port: TCP Port 23
• Unencrypted communications, visually/functionally similar to SSH.
• Mostly deprecated in favor of SSH.

Simple Mail Transfer Protocol (SMTP)

• Port: TCP Port 25
• Used for sending emails from one server to another.
• Configured on mail servers and some local devices.

Domain Name System (DNS)

• Port: UDP Port 53
• Translates domain names to IP addresses.
• Essential for network communication and redundancy.

Dynamic Host Configuration Protocol (DHCP)

• Ports: UDP Port 67, UDP Port 68
• Automatically assigns IP addresses and configuration.
• Can reserve specific IP addresses for particular devices.

Hypertext Transfer Protocol (HTTP/HTTPS)

• Ports: TCP Port 80 (HTTP), TCP Port 443 (HTTPS)
• HTTP is non-encrypted; HTTPS is encrypted.
• HTTPS is increasingly common for secure web communications.

Email Receiving Protocols

• POP3: TCP Port 110, Simple access to emails.
• IMAP4: TCP Port 143, Advanced features for managing emails across devices.

Server Message Block (SMB)

• Ports: TCP Port 445 (modern), TCP/UDP Port 139/137 (older NetBIOS)
• Used for file/printer sharing and Windows communication.

Lightweight Directory Access Protocol (LDAP/LDAPS)

• Ports: TCP Port 389 (LDAP), TCP Port 636 (LDAPS)
• Accesses directory services for network resources and user authentication.
• Common in use with Microsoft Active Directory.

Remote Desktop Protocol (RDP)

• Port: TCP Port 3389
• Allows remote access/control of Windows devices.
• Usable across multiple operating systems.

Conclusion

• Knowing and understanding port numbers and protocols is fundamental for network configuration and troubleshooting.
• These skills are crucial for IT professionals, particularly those pursuing A+ certification.