Question 1Core 1 · 2.0
A help desk needs to reach Windows desktops with Remote Desktop through an internal firewall. Which port must the firewall allow?
A+ ports and protocols
Ports are pure recall, and they appear on Core 1 every time. Learn them in families: file transfer, remote access, mail, names and addresses, web and Windows.
| Where it is tested | Core 1 (220-1201), Networking |
|---|---|
| How | Multiple choice, matching and firewall tasks |
The ports
| Port | Protocol | Use |
|---|---|---|
| 20, 21 TCP | FTP | File transfer (data, control) |
| 22 TCP | SSH | Encrypted remote shell; also SFTP |
| 23 TCP | Telnet | Unencrypted remote shell |
| 25 TCP | SMTP | Sending email |
| 53 TCP/UDP | DNS | Name resolution |
| 67, 68 UDP | DHCP | Address assignment (server, client) |
| 80 TCP | HTTP | Web, unencrypted |
| 110 TCP | POP3 | Downloading email |
| 137 to 139 | NetBIOS | Legacy Windows naming and sharing |
| 143 TCP | IMAP | Reading email on the server |
| 161, 162 UDP | SNMP | Device monitoring, traps |
| 389 TCP | LDAP | Directory lookups |
| 443 TCP | HTTPS | Web over TLS |
| 445 TCP | SMB | Windows file and printer sharing |
| 3389 TCP | RDP | Remote Desktop |
How to remember them
- Pair each clear-text protocol with its secure partner: Telnet 23 and SSH 22, HTTP 80 and HTTPS 443.
- Mail runs in order of the journey: SMTP 25 sends, POP3 110 downloads, IMAP 143 syncs.
- UDP for quick, small messages: DNS lookups, DHCP and SNMP.
Try 3 questions
Question 2Core 1 · 2.0
An administrator manages switches over Telnet and wants the same command-line access with the session encrypted. Which protocol and port should replace Telnet?
Question 3Core 1 · 2.0
Which DNS record type maps a host name to an IPv4 address?
Next step
Questions people ask
Which ports are on the A+ exam?
The common ones in the table: 20 and 21, 22, 23, 25, 53, 67 and 68, 80, 110, 137 to 139, 143, 161 and 162, 389, 443, 445 and 3389.
What port does Remote Desktop use?
TCP 3389.
What is the difference between POP3 and IMAP?
POP3 (110) downloads mail, usually to one device. IMAP (143) keeps it on the server, so every device stays in sync.