Common Network Port Numbers
By Chris Anderson · Updated Jul 10, 2026
Question catalog for this preview
Catalog listing of the 5 preview questions for this quiz.
Question 1
Which of the following ports are associated with email protocols? (Select ALL that apply)
Explanation
Port 25 (SMTP - server to server email), 110 (POP3 - retrieve email), 143 (IMAP - retrieve email with sync), and 587 (SMTP Submission - client to server with authentication) are all email-related ports. Ports 80 and 443 are HTTP/HTTPS web traffic.
Question 2
Which port is used by RDP (Remote Desktop Protocol)?
Explanation
RDP uses port 3389 by default to allow remote desktop connections, primarily to Windows systems. Port 5900 is VNC, port 3306 is MySQL, and port 8080 is often used as an alternate HTTP port.
Question 3
What port does LDAP (Lightweight Directory Access Protocol) use?
Explanation
LDAP uses port 389 for unencrypted directory queries. LDAPS (LDAP over SSL) uses port 636. Port 88 is Kerberos authentication. LDAP is commonly used to query Active Directory.
Question 4
Match each database system to its default port.
Explanation
MySQL=3306, PostgreSQL=5432, MSSQL=1433, Oracle=1521, MongoDB=27017. These database ports are critical to configure correctly in firewalls and connection strings. Exposing database ports directly to the internet is a major security risk.
Question 5
Match each protocol to its default port number.
Explanation
SSH=22, FTP Control=21, Telnet=23, SMTP=25, DNS=53. These are foundational port numbers every network professional should memorize. Notice SSH (22) is just one below Telnet (23) — SSH was designed as the secure replacement.