Quiz Entry - updated: 2026.07.14
What are the three port number groups and their ranges?
Well-Known: 0-1,023; Registered: 1,024-49,151; Dynamic/Private (ephemeral): 49,152-65,535.
* The 0-65,535 port space splits into three IANA ranges. *
Port Number Groups:
| Group | Range | Description |
|---|---|---|
| Well-Known Ports | 0 - 1,023 | Reserved for common services (HTTP, FTP, DNS) |
| Registered Ports | 1,024 - 49,151 | Assigned by IANA for specific applications |
| Dynamic/Private | 49,152 - 65,535 | Dynamically assigned as source ports |
Common Well-Known Ports:
| Port | Protocol | Application |
|---|---|---|
| 20, 21 | TCP | FTP (data/control) |
| 22 | TCP | SSH |
| 23 | TCP | Telnet |
| 25 | TCP | SMTP |
| 53 | UDP/TCP | DNS |
| 67, 68 | UDP | DHCP (server/client) |
| 69 | UDP | TFTP |
| 80 | TCP | HTTP |
| 110 | TCP | POP3 |
| 143 | TCP | IMAP |
| 161 | UDP | SNMP |
| 443 | TCP | HTTPS |
Group details:
- Well-Known (0-1,023): reserved for common server services; binding usually requires administrative privileges.
- Registered (1,024-49,151): assigned by IANA to specific applications a user installs (e.g., Cisco registered 1812 for RADIUS); no admin privilege required.
- Dynamic/Private (49,152-65,535): also called ephemeral ports; the client OS assigns them dynamically as source ports and releases them when the connection closes.
Memory tips:
- Well-Known = the original standardized services (first ~1024 ports).
- Registered = the "middle" range - neither reserved nor random.
- Dynamic = "49k and up" (49,152 = 3 × 2^14); temporary client source ports.
Go deeper:
RFC 6335 — IANA port number procedures — the document that formally defines these three ranges.- IANA Service Name and Port Number Registry — the live authoritative assignment list.
- List of TCP and UDP port numbers — handy Wikipedia lookup table for common ports.