30 questions · Tcp Udp Ports topic · All types, answers revealed
A technician is troubleshooting a VoIP phone that intermittently drops calls. The phone uses SIP (Session Initiation Protocol) for signaling and RTP (Real-time Transport Protocol) for audio. Which ports are typically used by these protocols?
SIP uses port 5060 for signaling, and RTP uses a dynamic UDP range for audio.
Port 53 is the standard port for DNS queries and zone transfers.
A company deploys a new internal application that uses a custom TCP port. The application fails to connect from client workstations. A technician verifies that the server is running and the firewall allows outbound traffic. Which step should the technician take next to identify the port issue?
Netstat shows listening ports and can confirm if the application is bound to the expected port.
Why this answer
To identify the port issue, the technician should use netstat to check if the server is listening on the expected port. Telnet to the port can test connectivity, but netstat shows listening services. Ping tests ICMP, not TCP.
DNS lookup resolves names, not ports. Netstat is the correct tool to verify port availability.
A user wants to access their company's webmail using a secure connection from a public Wi-Fi hotspot. The webmail server is configured to use IMAP over SSL. Which port should the email client use?
Port 993 is IMAPS, the secure version of IMAP using SSL/TLS.
Why this answer
IMAP over SSL (IMAPS) uses port 993. This provides encrypted access to email, protecting credentials and data on public networks.
A small office uses a network printer that supports both IPP and LPD printing. The printer is configured to use the default port for IPP. Which port must be open on the firewall for printing to work?
Port 631 is the default port for IPP, used for network printing.
Why this answer
Internet Printing Protocol (IPP) uses port 631 by default. Opening this port allows print jobs to be sent to the printer over the network.
A technician is troubleshooting a VoIP phone that cannot register with the SIP server. The phone has a valid IP address and can ping the server. Which port should be verified as open for SIP traffic?
Port 5060 is the default port for SIP traffic.
Why this answer
SIP (Session Initiation Protocol) typically uses port 5060 for unencrypted traffic and port 5061 for encrypted traffic. Port 80 is for HTTP, port 443 for HTTPS, and port 1720 for H.323. If port 5060 is blocked, SIP registration will fail.
During a security audit, a technician discovers that an internal web server is responding on port 8080 instead of the standard HTTP port. What is the most likely reason for this configuration?
Port 8080 is a common alternative for HTTP traffic, often used by proxy servers or when port 80 is blocked.
Why this answer
Port 8080 is commonly used as an alternative HTTP port, often for proxy servers or to avoid conflicts with standard port 80. It allows HTTP traffic without using the default port.
A customer reports that they cannot send emails from their desktop email client, but they can receive emails. The email server is running on the local network. Which port is most likely blocked on the firewall?
Port 25 is the default SMTP port for sending email; blocking it prevents outgoing mail.
Why this answer
SMTP uses port 25 for sending emails. If outgoing email fails but incoming works, port 25 is likely blocked. Port 110 (POP3) and 143 (IMAP) are for receiving email, and 993 is IMAPS (secure IMAP).
Port 80 (HTTP) and port 443 (HTTPS) are the standard ports for web traffic.
Why this answer
HTTP uses port 80 and HTTPS uses port 443. These are the standard ports for web traffic. Port 8080 is an alternate HTTP port, and 8443 is an alternate HTTPS port, but the question specifies standard ports.
Port 22 is the default SSH port, used for secure remote administration.
Why this answer
SSH (Secure Shell) uses port 22 by default for secure remote administration. Opening this port allows encrypted command-line access to the router.
A user needs to transfer files securely between two Linux servers over the internet. Which port should be allowed through the firewall for this purpose?
Port 22 is SSH, which SFTP uses for secure file transfers.
Why this answer
SFTP (SSH File Transfer Protocol) uses port 22, the same as SSH, for secure file transfers. It provides encryption and authentication.
A technician is configuring a remote desktop solution for a user who needs to access their Windows workstation from home. Which port must be forwarded on the router for RDP (Remote Desktop Protocol)?
Port 3389 is the default port for RDP, used for remote desktop connections to Windows.
A user cannot connect to a remote server using RDP. The network team confirms that the firewall allows outbound traffic on all ports. Which port is typically used for RDP and should be verified on the server side?
Port 3389 is the default port for Remote Desktop Protocol.
A technician is configuring a network monitoring tool that uses SNMP to query network devices. Which two ports should be allowed for SNMP communication?
Port 161 is for SNMP queries and port 162 for SNMP traps.
A user reports that they cannot send emails from their Outlook client, but they can receive emails. The email server is using standard ports. Which port is most likely blocked on the firewall?
Port 25 is SMTP, the standard port for sending email. Blocking it would prevent outgoing email while allowing incoming.
Why this answer
SMTP uses port 25 for sending email, while POP3 (port 110) or IMAP (port 143) are used for receiving. Blocking port 25 prevents outgoing email but not incoming.
A technician is configuring a new web server that must support both standard and encrypted web traffic. Which two ports should be opened in the firewall?
Port 80 handles HTTP and port 443 handles HTTPS, covering both standard and encrypted web traffic.
DNS requires TCP for zone transfers and large responses; blocking TCP port 53 can cause resolution failures.
A technician is setting up a network printer that supports both LPD (Line Printer Daemon) and IPP (Internet Printing Protocol). The printer must be accessible from Windows and Linux clients. Which port should be opened for IPP?
Port 631 is the standard port for IPP, used by both Windows and Linux.
UDP is unreliable and does not guarantee delivery or ordering, which can cause data loss under heavy load.
A technician is troubleshooting a legacy application that uses FTP for file transfers. The transfers work but are extremely slow. The network team mentions that the firewall is configured to inspect traffic on certain ports. Which port should be opened for FTP data transfer to improve performance?
Port 20 is the default data port for active FTP transfers.
Port 443 is HTTPS. Blocking it prevents secure web traffic while allowing unencrypted HTTP.
Why this answer
HTTPS uses port 443 for secure web traffic. If port 443 is blocked, HTTPS sites won't load, but HTTP (port 80) will still work.
A user reports that they cannot access a website hosted on a remote server. The technician finds that the firewall allows HTTP and HTTPS traffic, but the website uses a non-standard port. The user's browser shows 'connection refused'. Which tool can the technician use to verify if the remote port is open?
Telnet can connect to a specific port to verify if it is open and listening.
A user reports that they can receive emails but cannot send any. The email client is configured with SMTP on port 25. The IT team confirms that port 25 is blocked by the ISP. Which alternative port should be used for SMTP submission?
Port 587 is the standard SMTP submission port, often allowed by ISPs.
Why this answer
Many ISPs block port 25 to prevent spam. Port 587 is the standard SMTP submission port that is often unblocked. Port 110 is for POP3, port 143 for IMAP, and port 993 for IMAPS.
Using port 587 allows sending email when port 25 is blocked.
A user wants to securely transfer files to a remote server using a command-line tool. Which port is the default for SFTP (SSH File Transfer Protocol)?
SFTP uses SSH on port 22 for secure file transfer.
A security audit reveals that an internal file server is listening on multiple ports, including 137, 138, 139, and 445. The auditor recommends disabling older protocols. Which port is associated with SMB over TCP/IP directly (without NetBIOS)?
Port 445 is used by SMB directly over TCP/IP, without NetBIOS.
A technician is configuring a new database server that needs to accept remote connections from client applications using the default port for MySQL. Which port should be opened in the firewall?
Port 3306 is the default port for MySQL database connections.
Why this answer
MySQL uses port 3306 by default for client connections. Opening this port allows remote database access.
Port 67 is the DHCP server port, used to receive client requests and send offers.
A technician is setting up a network printer that supports both standard and secure printing. Which port should be configured for secure IPP printing?
Port 631 is the standard port for IPP, including secure IPP with encryption.
Why this answer
Secure IPP (Internet Printing Protocol) uses port 631 with encryption. Port 9100 is for raw printing (often HP JetDirect), port 515 for LPD, and port 443 for HTTPS but not specifically for printing. Port 631 is the correct choice for secure IPP.
A customer reports that they can browse the internet but cannot send or receive emails using their desktop email client. The email server is known to be working. Which port is most likely being blocked by a firewall?
Port 587 is the standard SMTP submission port for outgoing email.
During a network upgrade, a technician needs to allow remote desktop connections to Windows workstations from the internal network. Which port must be opened in the firewall?
Port 3389 is the default port for RDP, enabling remote desktop connections.
Why this answer
Remote Desktop Protocol (RDP) uses port 3389 by default. Opening this port allows remote desktop connections to Windows machines.
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