1645
RADIUS Authentication (old)
Medium RiskUDP — Security & VPN
Port Overview
Port Number
1645
Service Name
RADIUS Authentication (old)
Transport Protocol
UDP
Category
Security & VPN
Security Risk
Medium
Port Range
Registered (1024-49151)
What is Port 1645?
Port 1645 is an older, unofficial RADIUS authentication port used before the IANA officially assigned port 1812. Some legacy network devices and AAA servers still use this port for authentication. Network engineers managing older infrastructure may need to support both ports 1645 and 1812 simultaneously.
UDP
Security & VPN
Security Considerations
Port 1645 (RADIUS Authentication (old)) is classified as medium risk. While this service is commonly exposed, consider using encrypted alternatives where available.
Recommendation: Keep the service updated. Monitor logs for unusual activity.