CSLB General Building (B) — All Questions

Which TCP port is used by HTTPS web traffic by default?

• a.443✓
• b.80
• c.21
• d.25

HTTPS uses TCP port 443 for encrypted web traffic. Port 80 is plain HTTP, port 21 is FTP control, and port 25 is SMTP email.

What port does standard unencrypted HTTP use?

• a.443
• b.80✓
• c.53
• d.3389

HTTP serves web pages over TCP port 80. Port 443 is HTTPS, 53 is DNS, and 3389 is Remote Desktop Protocol.

Which protocol translates human-readable domain names into IP addresses?

• a.DHCP
• b.SMTP
• c.DNS✓
• d.SNMP

DNS resolves names like example.com into IP addresses. DHCP assigns addresses, SMTP sends email, and SNMP monitors network devices.

Which service automatically assigns IP addresses, subnet masks, and gateways to clients?

• a.DNS
• b.LDAP
• c.FTP
• d.DHCP✓

DHCP leases IP configuration to clients automatically. DNS handles name resolution, FTP transfers files, and LDAP provides directory services.

Which Wi-Fi standard, also known as Wi-Fi 6, operates in both 2.4 GHz and 5 GHz bands with improved efficiency?

• a.802.11ax✓
• b.802.11ac
• c.802.11n
• d.802.11g

802.11ax (Wi-Fi 6) improves efficiency and capacity and works in both 2.4 GHz and 5 GHz. 802.11ac is 5 GHz only, while 802.11n and 802.11g are older standards.

Which class of IPv4 address is 192.168.1.0/24 considered?

• a.Public routable
• b.Private (RFC 1918)✓
• c.Loopback
• d.APIPA

The 192.168.0.0/16 range is private per RFC 1918 and is not routable on the public internet. Loopback is 127.0.0.0/8, and APIPA uses 169.254.0.0/16.

A client shows an IP address in the 169.254.x.x range. What does this indicate?

• a.A static public IP
• b.A successful DHCP lease
• c.APIPA — the client failed to reach a DHCP server✓
• d.An IPv6 link-local address

An address in 169.254.0.0/16 is APIPA, which a Windows host self-assigns when no DHCP server responds. It signals a DHCP problem rather than a normal lease.

Which port is used by the Remote Desktop Protocol (RDP)?

• a.22
• b.161
• c.23
• d.3389✓

RDP listens on TCP port 3389. Port 22 is SSH, port 23 is Telnet, and 161 is SNMP.

Which protocol provides secure encrypted command-line access to a remote device?

• a.SSH✓
• b.Telnet
• c.FTP
• d.HTTP

SSH encrypts remote shell sessions on port 22. Telnet, FTP, and HTTP all send data, including credentials, in clear text by default.

What is the primary function of a router in a network?

• a.Amplify Wi-Fi signal only
• b.Forward packets between different networks✓
• c.Provide power over Ethernet
• d.Store shared files

A router forwards packets between separate networks, such as a home LAN and the internet, using IP addressing. Signal boosting, PoE, and file storage are handled by other devices.

Which cable type is required for 10 Gigabit Ethernet over reasonable copper distances?

• a.Cat 3
• b.Cat 5
• c.Cat 6a✓
• d.RG-6 coax

Cat 6a supports 10 Gbps over 100 meters. Cat 5 and Cat 3 cannot reliably carry 10 Gbps, and RG-6 is coaxial cable used for video/cable modems.

Which device operates primarily at Layer 2 and forwards frames based on MAC addresses?

• a.Hub
• b.Modem
• c.Router
• d.Switch✓

A switch learns MAC addresses and forwards frames only to the correct port at Layer 2. A hub blindly repeats to all ports, a router works at Layer 3, and a modem modulates signals for the ISP link.

What does NAT allow a home network to do?

• a.Share one public IP among many private devices✓
• b.Encrypt all traffic automatically
• c.Increase Wi-Fi range
• d.Assign DNS names

Network Address Translation lets multiple internal devices share a single public IP address. It is not an encryption, range-extension, or naming service.

Which protocol and port combination is used to send email between mail servers?

• a.POP3 on 110
• b.SMTP on 25✓
• c.IMAP on 143
• d.DNS on 53

SMTP on TCP port 25 transfers email between servers. POP3 (110) and IMAP (143) are used by clients to retrieve mail, and DNS resolves names.

A subnet mask of 255.255.255.0 corresponds to which CIDR notation?

• a./16
• b./8
• c./24✓
• d./32

255.255.255.0 sets the first 24 bits as the network portion, written as /24. /16 is 255.255.0.0, /8 is 255.0.0.0, and /32 is a single host.

Which wireless frequency band generally offers longer range but lower maximum speed?

• a.5 GHz
• b.60 GHz
• c.6 GHz
• d.2.4 GHz✓

The 2.4 GHz band penetrates walls better and reaches farther but supports lower throughput and has more interference. Higher bands like 5 GHz and 6 GHz offer more speed over shorter distances.

Which connector terminates a twisted-pair Ethernet cable?

• a.RJ45✓
• b.RJ11
• c.BNC
• d.SC

Ethernet twisted-pair cables use 8-position RJ45 connectors. RJ11 is for telephone lines, BNC is coax, and SC is a fiber-optic connector.

What is the purpose of a default gateway in IP configuration?

• a.Resolve domain names
• b.Route traffic destined for other networks✓
• c.Assign IP leases
• d.Filter spam

The default gateway is the router address a host sends traffic to when the destination is on another network. DNS resolves names and DHCP assigns leases.

Which command-line tool displays a device's current IP configuration on Windows?

• a.ping
• b.tracert
• c.ipconfig✓
• d.nslookup

ipconfig shows the local IP address, subnet mask, and gateway on Windows. ping tests reachability, tracert maps the route, and nslookup queries DNS.

Which protocol is used to synchronize the clocks of devices across a network?

• a.DHCP
• b.SNMP
• c.SMTP
• d.NTP✓

The Network Time Protocol (NTP) keeps device clocks synchronized, typically over UDP port 123. SNMP monitors devices, SMTP sends email, and DHCP assigns IP configuration.