Common Network Ports And Uses

Question 1

Telnet

Answer 1

TCP23, Login to devices remotely, console access, in-the-clear communication, not the best choice for production systems.

Question 2

SSH

Answer 2

(Secure Shell) TCP22, Login to devices remotely, console access, looks and acts same as telnet except data is encrypted.

Question 3

DNS

Answer 3

UDP53, Converts names to IP addresses. (Usually multiple DNS servers are in production)

Question 4

SMTP

Answer 4

(Simple Mail Transfer Protocol) TCP25, Server to server email transfer, also used to send mail from a device to a server, for incoming mail on device other protocols are used such as IMAP or POP3.

Question 5

SFTP

Answer 5

(Secure File Transfer Protocol) TCP22, Uses the SSH file transfer protocol, full feature file transfer (can resume transfer if interrupted, provide directory listing, remote file removals), encrypted with SSH.

Question 6

FTP

Answer 6

(File Transfer Protocol) TCP20 (Active mode data) TCP21 (control), transfers files between systems, requires authentication with username / pw, full-featured functionality (list, add, delete, etc.), not encrypted like SFTP

Question 7

TFTP

Answer 7

(Trivial File Transfer Protocol) UDP69, very simple file transfer application - read and write files, no authentication - not used on production systems.

Question 8

DHCP

Answer 8

(Dynamic Host Configuration Protocol) UDP67, UDP68, automated configuration of IP address, subnet mask, and other options, (requires a DHCP server - server, appliance, integrated into a SOHO router, etc.), (dynamic /pooled - IP addresses are assigned in real-time from a pool, each system is given a lease and must renew at set intervals), (DHCP reservation- addresses are assigned by MAC address in the DHCP server, quickly manage addresses from one location.)

Question 9

HTTP

Answer 9

(Hypertext Transfer Protocol) TCP80, communication in the browser and other applications, data sent in-the-clear.

Question 10

HTTPS

Answer 10

(Hypertext Transfer Protocol (Secured)) TCP443, communication in the browser and other applications that is encrypted.

Question 11

SNMP

Answer 11

(Simple Network Management Protocol) UDP161, gather statistics from network devices, Version 1 (The original) - structured tables, in-the-clear, Version 2 (A good step ahead) - Data type enhancements, bulk transfers, still in-the-clear, Version 3 (A secure standard) - message integrity, authentication, encryption.

Question 12

RDP

Answer 12

(Remote Desktop Protocol) TCP3389, share a desktop from a remote location, remote desktop services on many Windows versions, can connect to an entire desktop or just an application, clients for Windows, MacOS, Linux, Unix, iPhone, and others.

Question 13

NTP

Answer 13

(Network Time Protocol) UDP123, (switches, routers, firewalls, servers, workstations all have their own clocks), synchronizing the clocks becomes critical (log files, authentication details, outage information), automatic updates (flexible, you control how clocks are updated), very accurate (better than 1 millisecond on a local network).

Question 14

SIP

Answer 14

(Session Initiation Protocol) TCP5060, TCP5061, setup and manage VoIP sessions (call, ring, hang up), extend voice communication (video conference, instant messaging, file transfer, etc.)

Question 15

SMB

Answer 15

(Server Message Block (also called CIFS-Common Internet File System)) TCP445 (NetBIOS-less), protocol used by Microsoft Windows for file sharing, printer sharing, direct SMB communication over tcp445 without the NetBIOS transport

Question 16

POP

Answer 16

POP3 (Post Office Protocol version 3) TCP110, RECEIVE emails from an email server, authenticate and transfer, basic mail transfer functionality

Question 17

IMAP

Answer 17

IMAP4 (Internet Message Access Protocol Version 4) TCP143, most mobile devices today use this, includes management of email from multiple clients (desktop, mobile)

Question 18

LDAP / LDAPS

Answer 18

(Lightweight Directory Access Protocol) TCP389, store and retrieve information in a network directory. LDAPS (secure) TCP636, a non-standard implementation of LDAP over SSL

Question 19

H.323

Answer 19

(ITU telecommunication H.32x protocol series) TCP1720, setup and manage VoIP sessions (call, ring, hang up), one of the earliest VoIP protocols, many VoIP applications still use this today.