Ports and Protocols 1101

Match the protocol with its port number

• TELNET

• 22

• SMTP

• 25

• FTP

• 20, 21

• SSH

• 23

• DNS

• 53

Match the protocol with its port number

• 110

• POP3

• 80

• SNMP

• 137 - 139

• NETBIOS

• 67, 68

• HTTP

• 161, 162

• DHCP

Match the protocol with its port number

• LDAP

• 445

• SLP

• 143

• IMAP4

• 443

• SMB

• 389

• HTTPS

• 427

Match the protocol with its port number

• 989

• RDP

• 69

• AFP

• 548

• IMAPS

• 993

• TFTP

• 3389

• FTPS

SMB port #

• 422

• 465

• 445

• 587

You are running a performance test using three different browsers on the same computer to simultaneously access the same web site. What numeric identifier or address is used to keep the three connections separate at the application (browser) level? (a)  

• MAC Address
• Port number
• IP address
• FQDN

Answer explanation

The port number is used to identify the application or service running on the host. It is used to create a socket which is the combination of the IP address and the port number such as 192.168.1.1:8000. The IP address identifies the host, and the port number identifies the application or service running on the host. Since the three browsers are running on the same system, the socket will have the same IP address, but each will have a different port number to help keep the three connections or conversations separate. The source port number is assigned randomly, but the destination port number for the service being requested, HTTP (web server), is 80 (443 for HTTPS).

Jesenia read an article that said stored data, such as when you are downloading an app, is transmitted using TCP, but live-streaming events are transmitted using UDP. Why would this be true? Select two.

• TCP is reliable and ensures the delivery of data using a connection-oriented mechanism.

• UDP uses acknowledgements to ensure and guarantee the delivery of important data.

• UDP will retransmit data that has been lost during the transmission to guarantee delivery.

• UDP is fast and does not retransmit lost data so as not to disrupt the live video feed.

• Stored data is transmitted to a specific device, but live-stream data is sent to various devices.

Answer explanation

TCP (Transmission Control Protocol) is reliable and uses a connection-oriented mechanism to guarantee the delivery of data. It expects an acknowledgement from the destination. If it does not receive one, it resends the data.

. Live stream video feeds and real-time calls using Voice over IP are best delivered in a continuous stream so as not to disrupt the experience. If a live-stream video packet is lost, the video quality may be degraded for a second. If a voice packet is lost, the recipient could ask to repeat the statement.

. A restricted computer lab at a college has been set up with local authentication. Students are able to log in but do not have internet access. You check the network settings on one of the computers and it has an IP address of 169.254.1.10. What is the problem?

• The AAA server is not reachable

• The NAT server is not reachable

• The DNS server is not reachable

• The DHCP server is not reachable

Answer explanation

When a computer is configured to request an IP address from a DHCP server on power up, and the DHCP server is not available or reachable, the operating system will assign an address in the 169.254.x.y address space (APIPA, Automatic Private IP Addressing). This allows devices in the local network to have connectivity with each other but not with computers on another network, hence internet access is not possible. The host will transmit a DHCP discover message periodically in an attempt to obtain an address from a DHCP server

Quintavius loves to tinker with computers so he sets off to see how many networking services he can install in one physical server. He sets up the system to support DCHP, DNS, HTTP, HTTPS, Telnet, SSH, and an email server. On what port will these services listen?

• DCHP 67, DNS 53, HTTP 80, HTTPS 443, Telnet 23, SSH 22, SMTP 25

• DCHP 53, DNS 443, HTTP 80, HTTPS 23, Telnet 22, SSH 25, SMTP 67

• DCHP 443, DNS 23, HTTP 80, HTTPS 22, Telnet 25, SSH 67, SMTP 53

• DCHP 23, DNS 22, HTTP 80, HTTPS 25, Telnet 67, SSH 53, SMTP 443

Answer explanation

DHCP listens on port 67; it is used to assign IP addresses to computers automatically. DNS listens on port 53; it resolves domain names into IP addresses. HTTP listens on port 80; it serves online resources, but it is not secure. HTTPS listens on port 443; it serves web pages securely. Telnet listens on port 23; it is used for remote access, but transmissions are not encrypted so it is not secure. SSH listens on port 22 and is used for remote access. SSH is secure because the transmissions are encrypted. SMTP listens on port 25 and is used to send and receive email messages between email servers.

Suppose you wanted to run a publicly accessible website from your network server. For user activity from the auto-configured to access your website and bypass your firewall, you allow incoming traffic on port 80 on your router for this purpose. What is this process called?

• DMZ

• Keyword filtering

• Port forwarding

• IP filtering