Port 1812 (UDP) — RADIUS Authentication
Remote Authentication Dial-In User Service (RADIUS) on UDP/1812 (with accounting on UDP/1813) powers 802.1X enterprise Wi-Fi (WPA2/WPA3-Enterprise) and network switch port authentication.
| Port Number | 1812 |
|---|---|
| Transport Protocol | UDP |
| Primary Service | RADIUS Authentication |
| Standard / Specification | RFC 2865 |
| IANA Port Range | Registered User Port (1024–49151) |
| Internet Exposure Risk | Internal AAA security plane; restrict strictly to NAS switches, Wi-Fi controllers, and VPN gateways. |
Firewall Architecture & Hardening Best Practices
Use long, high-entropy shared secrets per network access device, isolate UDP/1812 on management VLANs, or encapsulate cross-WAN RADIUS inside RadSec (TCP/2083 TLS).
Operational Troubleshooting Note
Legacy Cisco configurations sometimes use UDP/1645 and UDP/1646—verify your FreeRADIUS or NPS listener ports match switch configs.
Quick CLI Connectivity & Firewall Reference
# Inspect local UDP/1812 socket binding on Linux ss -uapn | grep :1812 # Allow restricted CIDR on Linux UFW firewall ufw allow from 10.0.0.0/8 to any port 1812 proto udp
Planning firewall allowlists or VPN overlays? Use our IPv4 CIDR Calculator, MTU & TCP MSS Calculator, or WireGuard AllowedIPs Generator.
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