Port numbers

Question 1

FTP

Answer 1

tcp/20, tcp/21

Question 2

SSH

Answer 2

tcp/22

Question 3

Telnet

Answer 3

tcp/23

Question 4

SMTP

Answer 4

tcp/25

Question 5

DNS

Answer 5

udp/53, tcp/53

Question 6

DHCP

Answer 6

udp/67, udp/68

Question 7

HTTP

Answer 7

tcp/80

Question 8

HTTPS

Answer 8

tcp/443

Question 9

POP3

Answer 9

tcp/110

Question 10

IMAP4

Answer 10

tcp/143

Question 11

NetBIOS (name service)

Answer 11

udp/137

Question 12

NetBIOS (session service)

Answer 12

tcp/139

Question 13

SMB

Answer 13

tcp/445

Question 14

SNMP Query

Answer 14

udp/161

Question 15

SNMP Trap

Answer 15

udp/162

Question 16

LDAP

Answer 16

tcp/389

Question 17

RDP

Answer 17

tcp/3389

Question 18

What is FTP?

Answer 18

File Transfer Protocol

tcp/20 (active mode data) / tcp/21 (control)

• Transfers files between systems.
• Authenticates with a username and password (though some systems can use a generic/anonymous login)
• Full-featured functionality - list, add, delete, etc.

Question 19

What is SSH?

Answer 19

Secure Shell

tcp/22 (encrypted communication link)

• Looks and acts the same as Telnet

Question 20

What’s Telnet?

Answer 20

Telecommunication Network

tcp/23

• Login to devices remotely / gain console access
• In-the-clear communication (not the best choice for production systems)

Question 21

What is SMTP?

Answer 21

Simple Mail Transfer Protocol

tcp/25 (server-to-server email transfer)

• Also used to send mail from a device to a mail server
• Commonly configured on mobile devices and email clients
• Other protocols are used for clients to receive email (IMAP / POP3)

Question 22

What is DNS?

Answer 22

Domain Name System

udp/53

• Converts names to IP addresses
• These are super critical resources (usually multiple DNS servers are in production)

Question 23

What is DHCP?

Answer 23

Dynamic Host Configuration Protocol

udp/67, udp/68

• Automates configuration of an IP address, subnet mask, and other options (requires a DHCP server, can be integrated in to a server / appliance / SOHO router)
• Reserves by assigning IP address to the MAC address in the DHCP server. Makes it easy to manage addresses from one location

Question 24

What’s a dynamic IP address?

Answer 24

IP addresses are assigned in real-time from a pool using DHCP configuration. Each system is given a lease and must renew at set intervals.

Question 25

What’s HTTP and HTTPS?

Answer 25

Hypertext Transfer Protocol tcp/80 and tcp/443 (secure) - Provides communication within the browser / other apps - In-the-clear or encrypted - Supported by nearly all web servers and clients

Question 26

What is POP3?

Answer 26

Post Office Protocol version 3 tcp/110 - Receive (authenticate and transfer) emails from an email server - Basic mail transfer functionality

Question 27

What is IMAP4?

Answer 27

Internet Message Access Protocol version 4 tcp/143 - Receive (authenticate and transfer) emails from an email server - Includes email inbox management from multiple clients

Question 28

What is SMB?

Answer 28

Server Message Block tcp/445 - Protocol used by Windows for file sharing, printer sharing - Also called the CIFS (Common Internet File System)

Question 29

What is NetBIOS?

Answer 29

Network Basic Input/Output System udp/137 (nbname) - Register, remove, and find Windows services by name tcp/139 (nbsession) - Windows connection-oriented data transfer

Question 30

What is SNMP?

Answer 30

Simple Network Management Protocol udp/161 (queries), udp/162 (traps) - Gathers statistics from network devices - v1 was the original with structured tables, in-the-clear - v2 was a good step ahead, adding data type enhancements, bulk transfers, still in-the-clear - v3 became a secure standard, adding message integrity, authentication, encryption

Question 31

What is LDAP?

Answer 31

Lightweight Directory Access Protocol tcp/389 Stores and retrieves information in a network directory (commonly used in Microsoft Active Directory)

Question 32

What is RDP?

Answer 32

Remote Desktop Protocol tcp/3389 - Allows sharing a desktop from a remote location - Remote Desktop Services are on many Windows versions - Clients for Windows, macOS, Linux, Unix, iPhone, Android, and others