Port 1813 — UDP
RADIUS accounting records for network access sessions.
What is port 1813 used for?
RADIUS session accounting.
Transport protocol
UDP
Security precautions
Restrict access to authorized network access devices and accounting servers.
Should we open this port in the firewall?
Allow this port only when a required service uses it. Apply least privilege: restrict authorized sources, destinations and interfaces, and log connections where appropriate.
How do I check this port?
Test-NetConnection -Port tests TCP, not UDP. Generate an authorized test access session and confirm Accounting-Start, interim updates where configured, and Accounting-Stop in server logs.
Capture UDP 1813 during a real application exchange and verify the request and response. UDP has no TCP-style handshake; a missing reply to a generic probe does not prove that the port is closed.
Port-to-service mappings are common conventions. Applications can use a different configured port; confirm the actual service and transport.