220-1201 TCP & UDP Ports — All Questions With Answers

Question 1

A small office reports that internal users can access the internet but cannot resolve domain names to IP addresses. The DNS server is configured correctly. Which port should be checked on the firewall?

Accepted Answer

Port 53. DNS uses port 53 for both TCP and UDP. If port 53 is blocked, DNS queries will fail, causing name resolution issues. Port 80 is for HTTP, port 443 for HTTPS, and port 67 for DHCP. Blocking port 53 prevents DNS resolution while allowing other traffic.

Answer

Port 80

Answer

Port 443

Answer

Port 67

Question 2

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?

Accepted Answer

Run netstat on the server to see if the application is listening on the correct port.. 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.

Answer

Ping the server from a client to test network connectivity.

Answer

Use nslookup to verify the server's hostname resolves correctly.

Answer

Check the DHCP lease to ensure the client has a valid IP address.

Question 3

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?

Accepted Answer

Port 5060. 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.

Answer

Port 80

Answer

Port 443

Answer

Port 1720

Question 4

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?

Accepted Answer

Port 3389. RDP (Remote Desktop Protocol) uses port 3389 by default. Port 22 is for SSH, port 23 for Telnet, and port 5900 for VNC. If the server's firewall is not allowing inbound traffic on port 3389, the RDP connection will fail.

Answer

Port 22

Answer

Port 23

Answer

Port 5900

Question 5

A technician is configuring a network monitoring tool that uses SNMP to query network devices. Which two ports should be allowed for SNMP communication?

Accepted Answer

Port 161 and 162. SNMP uses port 161 for queries (GET/SET) and port 162 for traps (notifications). Port 161 is used by the agent to receive requests, and port 162 is used by the manager to receive traps. Ports 22 and 23 are for SSH and Telnet, 80 and 443 for web, 67 and 68 for DHCP.

Answer

Port 22 and 23

Answer

Port 80 and 443

Answer

Port 67 and 68

Question 6

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?

Accepted Answer

Port 80 and 443. Standard web traffic uses port 80 (HTTP) and encrypted web traffic uses port 443 (HTTPS). Port 22 is for SSH, port 21 for FTP, and port 3389 for RDP.

Answer

Port 22 and 21

Answer

Port 3389 and 5900

Answer

Port 53 and 123

Question 7

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?

Accepted Answer

Port 20. FTP uses two ports: port 21 for control commands and port 20 for data transfer. If port 20 is blocked or inspected heavily, data transfer will be slow. Port 22 is for SFTP (SSH FTP), port 23 for Telnet, and port 69 for TFTP. Opening port 20 allows faster data transfer.

Answer

Port 22

Answer

Port 23

Answer

Port 69

Question 8

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?

Accepted Answer

Port 587. 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.

Answer

Port 110

Answer

Port 143

Answer

Port 993

Question 9

A technician is setting up a network printer that supports both standard and secure printing. Which port should be configured for secure IPP printing?

Accepted Answer

Port 631. 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.

Answer

Port 9100

Answer

Port 515

Answer

Port 443

Question 10

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?

Accepted Answer

Port 587. Email submission typically uses port 587 for SMTP with STARTTLS, or port 25 for unencrypted SMTP. Port 80 is HTTP, port 443 is HTTPS, and port 110 is POP3 for receiving email. Blocking port 587 would prevent outgoing email while allowing web browsing.

Answer

Port 80

Answer

Port 443

Answer

Port 110

Question 11

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?

Accepted Answer

SIP: 5060, RTP: 16384-32767. SIP typically uses port 5060 (UDP or TCP) for signaling, and RTP uses a range of UDP ports (often 16384-32767) for audio streams. Port 80 is HTTP, port 443 is HTTPS, and port 1720 is H.323 (another VoIP protocol).

Answer

SIP: 80, RTP: 443

Answer

SIP: 1720, RTP: 5060

Answer

SIP: 443, RTP: 80

Question 12

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?

Accepted Answer

25. 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).

Answer

110

Answer

143

Answer

993

Question 13

A technician is configuring a new web server that must support both standard HTTP and HTTPS traffic. Which two ports should be opened in the firewall?

Accepted Answer

80 and 443. 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.

Answer

21 and 22

Answer

8080 and 8443

Answer

25 and 110

Question 14

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)?

Accepted Answer

3389. RDP uses TCP port 3389 by default. Port 22 is SSH, port 5900 is VNC, and port 443 is HTTPS. RDP is the standard for Windows remote desktop.

Answer

22

Answer

5900

Answer

443

Question 15

A company's internal DNS server is not resolving hostnames for clients. The technician verifies that the DNS service is running and the firewall allows traffic on port 53. However, clients still cannot resolve names. What is the most likely issue?

Accepted Answer

The firewall is blocking TCP port 53. DNS uses both UDP and TCP on port 53. UDP is used for standard queries, but TCP is necessary for zone transfers or large responses. If only UDP is allowed, some DNS operations may fail. Port 53 is correct, but the protocol type matters.

Answer

The firewall is blocking UDP port 53

Answer

The DNS server is using port 5353 instead of 53

Answer

Clients are using the wrong DNS server IP

Question 16

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?

Accepted Answer

631. IPP uses TCP port 631. LPD uses port 515. Port 9100 is used by some HP printers for direct printing (JetDirect). Port 80 is HTTP, which is not typically used for printing.

Answer

515

Answer

9100

Answer

80

Question 17

A network administrator notices that a critical database server is responding slowly. The server uses both TCP and UDP for different services. Which of the following is a characteristic of UDP that could explain performance issues under heavy load?

Accepted Answer

UDP does not guarantee packet delivery or order. UDP is connectionless and does not guarantee delivery, so it does not retransmit lost packets. Under heavy load, packet loss can increase without recovery, causing application-level issues. TCP retransmits lost packets, which can add latency but ensures delivery.

Answer

UDP retransmits lost packets automatically

Answer

UDP uses a three-way handshake to establish a connection

Answer

UDP provides flow control to prevent congestion

Question 18

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?

Accepted Answer

Telnet. Telnet can be used to test connectivity to a specific port (e.g., telnet example.com 8080). Ping uses ICMP, not TCP ports. Nslookup tests DNS resolution. Tracert traces the route but does not test port status.

Answer

Ping

Answer

Nslookup

Answer

Tracert

Question 19

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)?

Accepted Answer

22. SFTP runs over SSH, which uses port 22 by default. Port 21 is for standard FTP, port 20 is FTP data, and port 990 is FTPS (FTP over SSL).

Answer

21

Answer

20

Answer

990

Question 20

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)?

Accepted Answer

445. Port 445 is used by SMB directly over TCP/IP (also known as SMB over TCP). Ports 137-139 are used by NetBIOS over TCP/IP, which is older and less secure. Port 443 is HTTPS, and port 21 is FTP.

Answer

137

Answer

139

Answer

443

220-1201 TCP & UDP Ports — All Questions With Answers

A small office reports that internal users can access the internet but cannot resolve domain names to IP addresses. The DNS server is configured correctly. Which port should be checked on the firewall?

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?

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?

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?

A technician is configuring a network monitoring tool that uses SNMP to query network devices. Which two ports should be allowed for SNMP communication?

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?

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?

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?

A technician is setting up a network printer that supports both standard and secure printing. Which port should be configured for secure IPP printing?

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?

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?

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?

A technician is configuring a new web server that must support both standard HTTP and HTTPS traffic. Which two ports should be opened in the firewall?

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)?

A company's internal DNS server is not resolving hostnames for clients. The technician verifies that the DNS service is running and the firewall allows traffic on port 53. However, clients still cannot resolve names. What is the most likely issue?

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?

A network administrator notices that a critical database server is responding slowly. The server uses both TCP and UDP for different services. Which of the following is a characteristic of UDP that could explain performance issues under heavy load?

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)?

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)?

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?

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?

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?

A network administrator needs to allow secure remote administration of a router using SSH. The router is configured to use the default SSH port. Which port must be opened on the firewall?

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?

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?

A customer complains that their web browser cannot load any HTTPS websites, but HTTP sites work fine. The firewall is configured to allow common ports. Which port is most likely being blocked?

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?

A technician is troubleshooting a DHCP issue where clients are not receiving IP addresses. Which port must be open on the firewall for DHCP server communication?

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?

220-1201 TCP & UDP Ports — All Questions With Answers

A small office reports that internal users can access the internet but cannot resolve domain names to IP addresses. The DNS server is configured correctly. Which port should be checked on the firewall?

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?

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?

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?

A technician is configuring a network monitoring tool that uses SNMP to query network devices. Which two ports should be allowed for SNMP communication?

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?

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?

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?

A technician is setting up a network printer that supports both standard and secure printing. Which port should be configured for secure IPP printing?

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?

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?

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?

A technician is configuring a new web server that must support both standard HTTP and HTTPS traffic. Which two ports should be opened in the firewall?

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)?

A company's internal DNS server is not resolving hostnames for clients. The technician verifies that the DNS service is running and the firewall allows traffic on port 53. However, clients still cannot resolve names. What is the most likely issue?

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?

A network administrator notices that a critical database server is responding slowly. The server uses both TCP and UDP for different services. Which of the following is a characteristic of UDP that could explain performance issues under heavy load?

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)?

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)?

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?

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?

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?

A network administrator needs to allow secure remote administration of a router using SSH. The router is configured to use the default SSH port. Which port must be opened on the firewall?

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?

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?

A customer complains that their web browser cannot load any HTTPS websites, but HTTP sites work fine. The firewall is configured to allow common ports. Which port is most likely being blocked?

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?

A technician is troubleshooting a DHCP issue where clients are not receiving IP addresses. Which port must be open on the firewall for DHCP server communication?

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?