Network Protocols, Ports and Services
A+ networking questions test common protocols, ports, IP addressing, DNS, DHCP, network service roles, and command-line verification.
How to study for CompTIA A+
Treat each A+ item as a support decision: identify the device, symptom, layer, safest next step, user impact, and documentation requirement.
Core concepts
Concept 1
Protocols and ports identify how applications communicate and where traffic should be allowed or investigated.
Exam cue: Use the protocol and port to infer the service.
Concept 2
DNS, DHCP, IP addressing, subnet masks, gateways, and name resolution are core troubleshooting anchors.
Exam cue: Check IP, mask, gateway, and DNS before replacing hardware.
Concept 3
Network services must be matched to the symptom before changing adapters, routers, or firewalls.
Exam cue: Separate name resolution failure from connectivity failure.
Risk pitfalls and guardrails
Troubleshooting DNS when the device has no valid IP address.
Guardrail: Avoid answers that skip verification, expose user data, ignore recent changes, replace parts too early, or bypass policy for convenience.
Opening a port without understanding the service risk.
Guardrail: Avoid answers that skip verification, expose user data, ignore recent changes, replace parts too early, or bypass policy for convenience.
Confusing private addressing, APIPA, and public routable addressing.
Guardrail: Avoid answers that skip verification, expose user data, ignore recent changes, replace parts too early, or bypass policy for convenience.
Memory anchors
DNS
DNS resolves names to IP addresses and can cause name-only connectivity failures.
DHCP
DHCP automatically assigns IP configuration such as address, mask, gateway, and DNS.
APIPA
APIPA self-assigns a 169.254.x.x address when DHCP fails on an IPv4 client.
Gateway
A default gateway routes traffic from the local network to other networks.
Subnet Mask
A subnet mask identifies which part of an IP address is local network information.
HTTPS
HTTPS uses encrypted web communication, commonly over TCP port 443.
SSH
SSH provides encrypted remote command-line access, commonly over TCP port 22.
SMB
SMB supports Windows file and printer sharing, commonly over TCP port 445.
IMAP
IMAP retrieves email while leaving messages on the server for synchronization.
SMTP
SMTP sends email between clients and mail servers or between mail servers.
Checkpoint rule
Do the check-up only after you can summarize each concept in one sentence and identify one dangerous pitfall from memory.
Knowledge Check (after reading)
Short check-up to confirm understanding of this module.
Check-up Questions
A workstation can reach a web server by IP address but not by its host name. Which network service should the technician investigate first?
A Windows user cannot open a shared folder after a firewall rule change, while other network services work. Which protocol should be allowed?
Answer all questions to submit.
Next step personalized recommendations
Continue learning
Move forward only after this module is stable.
What is Pass Harbor?
Completely free exam prep for 317 U.S. exams.
- Practice questions
- Flashcards
- Study guides
- Mock exams
- No registration
- No paywall
- Start instantly
“No more expensive exam prep. Quality study tools should be accessible to everyone.”