CompTIA A+ sample questions, with worked answers

A: The PC's cable and network connection to the DHCP server. A 169.254 address means the PC did not get a reply from DHCP. A bad cable or port is the first thing to rule out.

The trap: Looking at DNS because "nothing works". A 169.254 address means the PC never got an address from DHCP, so start with its own connection.

B: Wi-Fi 6E. Wi-Fi 6E extends 802.11ax into the 6 GHz band.

A: SMTP. SMTP sends email from a client to a server and between mail servers.

A: 30. A /27 leaves 32 − 27 = 5 host bits, which give 2⁵ = 32 addresses. Two are reserved (network and broadcast), so 30 hosts.

1. Host bits: 32 − 27 = 5.
2. Addresses: 2⁵ = 32.
3. Usable: 32 − 2 = 30.

The trap: Answering 32 and forgetting that the network and broadcast addresses cannot be given to hosts.

A: 53. Name resolution uses DNS on port 53. Sites load by IP address, so web traffic (80 and 443) is getting through; only the name lookups are failing.

1. By IP works: the web ports are open.
2. By name fails: name resolution is broken.
3. Name resolution is DNS, port 53.

The trap: Choosing 443 because "websites" are failing. If HTTPS were blocked, the IP address would not work either.

B: 802.11ax. 802.11ax is Wi-Fi 6 (and Wi-Fi 6E when it uses the 6 GHz band). 802.11ac is Wi-Fi 5 and 802.11n is Wi-Fi 4.

1. Wi-Fi 4 = 802.11n.
2. Wi-Fi 5 = 802.11ac.
3. Wi-Fi 6 = 802.11ax.

The trap: Picking 802.11ac because it was the fast standard for years. It is Wi-Fi 5.

C: Back up the data immediately. Clicking suggests the drive is failing; save the data before anything else.

The trap: Running a repair tool first. Clicking means the drive may die at any moment, and the data is worth more than the drive.

A: 16 TB. RAID 5 gives up one drive's worth of space to parity: (5 − 1) × 4 TB = 16 TB.

C: gives wide viewing angles and accurate color, with a backlight. IPS LCD: gives wide viewing angles and accurate color, with a backlight.

C: does not show a newly installed drive in the firmware setup. When a computer does not show a newly installed drive in the firmware setup, the usual suspect is an incorrect drive cable or controller setting.

B: 4 TB. RAID 10 stripes across mirrored pairs, so half the raw space holds copies: 4 × 2 TB = 8 TB raw, and half of that, 4 TB, is usable.

1. Raw space: 4 × 2 TB = 8 TB.
2. RAID 10 mirrors every drive, so usable space is half the raw space.
3. 8 TB ÷ 2 = 4 TB.

The trap: Answering 6 TB, which is RAID 5 (one drive's worth for parity). RAID 10 always gives half.

A: The phone charger cannot supply enough power for the laptop. USB-C Power Delivery negotiates wattage, and a 20 W charger cannot meet a laptop that needs about 65 W. It works with its own adapter, so the battery and port are fine.

1. It charges normally from its own adapter: the battery and port work.
2. The phone charger supplies 20 W; the laptop expects about 65 W.
3. Too little power means slow or no charging.

The trap: Blaming the battery. The laptop charges fine from its own adapter, which rules the battery out.

C: SaaS. Software as a service delivers a finished application over the internet, with the provider managing the servers, the operating system and the app itself.

1. Ask who manages the application: the provider.
2. The office only uses the app in a browser.
3. A finished application from a provider is SaaS.

The trap: Choosing IaaS because "servers moved to the cloud". With IaaS the customer still manages the operating system and the software.

B: Test the theory to determine the cause. The order is: identify the problem, establish a theory, test the theory, establish a plan and implement it, verify full functionality, then document.

1. Step 1, identify the problem: done.
2. Step 2, establish a theory: done.
3. Step 3: test the theory.

The trap: Jumping to the fix. If the test does not confirm the theory, you go back and form a new one.

A: The fuser. The fuser melts toner onto the paper with heat and pressure. If it is not hot enough, the toner sits on the surface and smears.

1. Toner is on the page, so imaging and transfer worked.
2. It is not bonded, so the bonding step failed.
3. Bonding is the fuser's job.

The trap: Blaming the drum. A drum fault shows as repeating marks or lines, not toner that rubs off.

B: WPA2- or WPA3-Enterprise with a RADIUS server. Enterprise mode authenticates each user through RADIUS instead of one shared key.

The trap: Choosing WPA2-Personal because it is encrypted. Personal mode uses one shared passphrase, not each user's own credentials.

C: Credential stuffing. Credential stuffing tries username and password pairs exposed in a breach of another site.

B: Use the drive's secure erase function. A secure erase (or a manufacturer sanitize command) clears every cell on an SSD, including spare areas, and leaves the drive reusable. Degaussing does not work on flash memory, and deleting or quick formatting leaves recoverable data.

1. The drives must stay usable, so physical destruction is out.
2. SSDs store data in flash, which degaussing does not affect.
3. A secure erase clears all cells and keeps the drive working.

The trap: Choosing degaussing. It wipes magnetic hard drives (and ruins them) but does nothing to an SSD.

B: Phishing; report it to the security team and do not reply. An urgent request for money that impersonates an executive is phishing (often called whaling or business email compromise). Report it so others are warned, and do not reply or act on it.

1. Spot the signs: urgency, an unusual request, money.
2. It impersonates a trusted person: phishing.
3. Report it and do not engage.

The trap: Deleting it quietly. Reporting it lets the security team warn others who got the same email.

D: exFAT. exFAT is read and written by both systems and has no 4 GB file-size limit.

The trap: Choosing FAT32 because "it works everywhere". It does, but it cannot hold a file over 4 GB.

D: changes display, network and user options. System Settings (System Preferences) changes display, network and user options.

C: sets security rules for organizations that handle payment card data. PCI DSS sets security rules for organizations that handle payment card data.

A: Remove the USB drive and check the boot order. If the firmware tries to boot from a non-bootable USB drive first, it can report no boot device. Removing the drive and checking the boot order is the quickest, least drastic test.

1. Something changed: a USB drive is plugged in.
2. Firmware may be trying to boot from it.
3. Remove it and check the boot order before anything drastic.

The trap: Replacing the drive. Start with the simplest cause that fits the symptom and the recent change.

B: Windows Pro. Joining a domain needs Pro or higher (Pro, Enterprise or Education). Home editions cannot join an Active Directory domain.

1. Domain join is a business feature.
2. Home editions do not include it.
3. Pro is the lowest edition that does.

The trap: Thinking any edition can join if you have an admin password. Home simply does not have the feature.

B: chkdsk /f. chkdsk checks a volume's file system, and /f tells it to fix errors. sfc repairs protected system files, a different job.

1. The task is the file system on a drive.
2. chkdsk checks disks; /f fixes errors.
3. sfc is for system files, not the disk.

The trap: Choosing sfc /scannow, which repairs Windows system files, not the file system on the disk.

B: Sunday's full and Thursday's differential. A differential holds every change since the last full backup, so Thursday's differential already includes Monday to Wednesday. You need the full plus the latest differential.

1. Differential = all changes since the last full.
2. Thursday's differential covers Monday to Thursday.
3. Restore Sunday's full, then Thursday's differential.

The trap: Answering every backup since Sunday. That is the rule for incremental backups, which hold only the changes since the previous backup.