CompTIA A+ 220-1101 | 2.1 Port Numbers (Detailed)

Reviews Common Port Numbers

File Transfer Protocol (FTP)

• Transfers files from one client to another

• Allows for full file management functions

• Operates on in Transfer Control Protocol (TCP)

  • TCP/20 - allows for data transfer

  • TCP/21 - controls that data transfer

Secure Shell Host (SSH)

• Allows for text based connection to a terminal with encryption

• Operates in Transfer Control Protocol (TCP)

  • TCP/22 - enables secure remote access

Telnet

• Allows for text based terminal connection without encryption

• Operates in Transfer Control Protocol (TCP)

  • TCP/23 - enables remote access

Simple Mail Transfer Protocol (SMTP)

• Allows client to send mail to a mail server

• Operates in Transfer Control Protocol (TCP)

  • TCP/25 - enables email transmission

Domain Name System (DNS)

• Converts common site names to accessible IP addresses

• Operates User Datagram Protocol (UDP)

  • UDP/53

Dynamic Host Configuration Protocol (DHCP)

• Auto assigns IP addresses to devices once connected to network

• Can work on a leasing system, which requires renewal of IP registration

• Reservations can be made, which allows for specific devices to receive specific IP address every time it connects

• Requires a DHCP server

• Operates in User Datagram Protocol (UDP)

  • UDP/67 and UDP/68 - facilitates dynamic IP address assignment

Hyper Text Transfer Protocol (HTTP)

• Allows for transfer of information via the internet

• Operates in Transmission Control Protocol (TCP)

  • TCP/80 - enables web page loading

Hyper Text Transfer Protocol Secure (HTTPS)

• Allows for transfer of information via the internet, with encryption

• Operates in Transmission Control Protocol (TCP)

  • TCP/443 - secures data transmission over the web

Server Message Block AKA Common Internet File System (SMB/CIFS)

• The modern protocol

• Used by Windows

• Allows for transfer of files between clients using the same operating system, and shared resources like printers and other networked devices

• Operates in Transmission Control Protocol (TCP)

  • TCP/445

NetBios

• The older SMB protocol

• Operates on both TCP and UDP

  • TCP/139 - sets up session and allows for data transfer between devices

  • UDP/137 - names networked services so devices can be found by name on the network

Lightweight Directory Access Protocol (LDAP)

• Allows query (search) of directory

• Examples: Active Directory

• Operates in Transmission Control Protocol (TCP)

  • TCP/389

Post Office Protocol v3 (POP3)

• Allows for retrieval of emails on one client

• Operates in Transmission Control Protocol (TCP)

  • TCP/110
    

Internet Message Access Protocol (IMAP)

• Allows for inbox management from multiple clients

• Operates in Transmission Control Protocol (TCP)

  • TCP/143

Simple Network Management Protocol (SNMP)

• Allows management devices to query infrastructure devices for performance statistics, and receives the results in return

  • Queries are done on port UDP/161

  • Alerts, which can be configured to trigger when certain circumstances are met, occur on port UDP/162

• There are three versions

  • v1

    • Original version

    • Unencrypted

  • v2

    • Allowed for bulk transfer

    • Unencrypted

  • v3

    • Encrypted

    • Guarantees authentication, and message integrity

Remote Desktop (RDP)

• Allows for remote assistance to target client

• Operates on Transmission Control Protocol (TCP)

  • TCP/3389