220-1101 TCP & UDP Ports — 10 Questions

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