Study Ports, Protocols and Common Services for A+ Core 1 (220-1201)
Learn the high-value network protocols, ports, and service behaviors that A+ Core 1 expects for support and SOHO troubleshooting.
A+ Core 1 does not need full protocol depth, but it does expect you to know which common service or port matches the job. The best answers usually come from matching the protocol to the business need, not from memorizing raw numbers with no context.
Port: A logical endpoint that lets multiple services share one IP address cleanly.
Protocol: The communication rule set that tells systems how to format, send, and interpret traffic.
What CompTIA is really testing
CompTIA usually wants you to:
- identify the service behind the symptom
- remember the highest-value common ports
- know which protocol choice is more secure or supportable
High-yield service map
| Service | Port | Why it matters |
|---|---|---|
| SSH | 22 |
secure remote terminal access |
| HTTP / HTTPS | 80 / 443 |
ordinary and encrypted web traffic |
| DNS | 53 |
hostname resolution |
| DHCP | 67 / 68 |
automatic IP configuration |
| RDP | 3389 |
remote desktop access |
| SMTP / IMAP / POP3 | 25/587, 143/993, 110/995 |
mail sending and retrieval |
| LDAP / LDAPS | 389 / 636 |
directory and identity lookups |
Service family thinking is faster than raw memorization
| If the question is really about… | Think first about… |
|---|---|
| secure remote command-line access | SSH |
| ordinary secure web access or web admin | HTTPS |
| hostname lookup | DNS |
| auto-addressing on a LAN | DHCP |
| remote desktop session | RDP |
| directory or identity lookup | LDAP or LDAPS |
A small support example
1User symptom: "I can reach the server by IP, but not by name."
2Strong lane: DNS
3Not the first lane: RDP, SMTP, or random cable replacement
What to notice:
- user symptoms usually map to one service family first
- you do not need deep protocol internals to choose the right support lane
- one correct service match eliminates several flashy wrong answers
Security and support clues
When A+ offers an older protocol and a more secure newer one, the stronger support answer usually favors the safer choice:
SSHover TelnetHTTPSover plain HTTP for secure web management- encrypted mail or directory variants when the scenario calls for secure handling
Harder scenario question
A technician can reach a router’s management IP in the browser, but the prompt explicitly says the session must be encrypted. Another answer choice suggests Telnet because it is also a remote management protocol.
The stronger answer usually:
- stays with the actual task instead of the broader category
- notices the security requirement
- prefers the secure protocol, not just any protocol that can reach the device
Common traps
- mixing service purpose and port number
- treating secure and insecure protocol variants as interchangeable
- choosing a protocol because it sounds familiar instead of because it fits the task
What strong answers usually do
- connect the user action to the actual service behind it
- remember the high-value ports that appear repeatedly
- prefer the more secure option when the scenario explicitly cares about protection
- use the symptom to narrow the protocol lane before staring at answer choices