Ports 1000–1999

Port 1194 — OpenVPN

At a Glance

• Transport: UDP or TCP

• Common service: OpenVPN

• Main purpose: Encrypted VPN tunnels

• Status: Common default, current

• Related ports: 443

What It Does

Port 1194 is OpenVPN's registered default for TCP and UDP; UDP is common. Administrators may configure other ports, including TCP 443, when network policy requires it.

ELI Explains Secret underground tunnel between house and office. Travel privately — nobody above sees. Invisible and encrypted.

A 10-Year-Old's Example Two boxes with a secret tube. Whisper in yours, travels through, friend hears. OpenVPN is that secret tube.

Remember This Port 1194 is a common OpenVPN default — encrypted tunnels for remote access.

Port 1433 — Microsoft SQL Server

At a Glance

• Transport: TCP

• Common service: Microsoft SQL Server

• Main purpose: Database connections

• Status: Official, current

• Related ports: 1434

What It Does

Default MS SQL Server port. Applications query databases here. Named instances use dynamic ports via SQL Browser (UDP 1434).

ELI Explains Librarian's desk at a giant library. "Need data X." Librarian fetches from organized shelves. 1434 helps find other doors.

A 10-Year-Old's Example Filing cabinet manager: "Folder 42, Page 3." Finds it, hands it over. Port 1433 is that manager.

Remember This Default MS SQL Server port. Restrict to app servers, enable TLS.

Security Note Never expose directly to the internet.

Port 1701 — L2TP

At a Glance

• Transport: UDP

• Common service: Layer 2 Tunneling Protocol

• Main purpose: VPN tunnel creation

• Status: Official, current

• Related ports: 500, 4500

What It Does

Creates VPN tunnels but has no encryption. Always paired with IPsec for security. Together: L2TP/IPsec.

ELI Explains Digging a tunnel without doors. Anyone could walk through. IPsec adds locked doors. Never use L2TP alone.

A 10-Year-Old's Example Secret passage between treehouses, no door. Add locked hatches (IPsec). Passage (L2TP) alone is useless.

Remember This L2TP has no encryption. Always pair with IPsec.

Port 1812 — RADIUS Authentication

At a Glance

• Transport: UDP

• Common service: RADIUS Authentication

• Main purpose: Centralized network access auth

• Status: Official, current

• Related ports: 1813

What It Does

Handles Wi-Fi, VPN, and device authentication. Access devices send credentials; RADIUS checks directory and responds accept/reject.

ELI Explains Central ID office for campus. Every entrance radios "badge valid?" here. One place manages all access.

A 10-Year-Old's Example One security desk, intercoms at every side entrance. Buzz in, guard checks master list. RADIUS is that desk.

Remember This RADIUS (1812) centralizes network auth. Accounting on 1813 tracks sessions.

Port 1813 — RADIUS Accounting

At a Glance

• Transport: UDP

• Common service: RADIUS Accounting

• Main purpose: Tracks user sessions

• Status: Official, current

• Related ports: 1812

What It Does

Records session start/stop, data transferred. 1812 answers "can they connect?" 1813 tracks "how long did they stay?"

ELI Explains 1812 = guard checking IDs. 1813 = logbook of when each person entered and left.

A 10-Year-Old's Example Library sign-in: arrived 10:15, left 11:00. RADIUS accounting is that sign-in sheet.

Remember This RADIUS accounting tracks sessions — who connected and for how long.

Port 1883 — MQTT

At a Glance

• Transport: TCP

• Common service: Message Queuing Telemetry Transport

• Main purpose: Lightweight IoT messaging

• Status: Official, current

• Related ports: 8883

What It Does

Publish-subscribe for low-bandwidth networks. IoT backbone — sensors, smart homes, industrial monitoring.

ELI Explains Bulletin board by topic. Sensors pin to "temperature." Devices check their boards. Better than every device calling every other.

A 10-Year-Old's Example Classroom boards: "Weather," "Sports." Check "Sports" for updates. Announcer pins scores. MQTT is those boards.

Remember This MQTT: lightweight IoT messaging. Use 8883 for encrypted MQTT.