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RADIUS Accounting
Port 1646 is primarily used by RADIUS accounting services, often involving Cisco and Juniper Networks devices. It facilitates the transmission of user accounting information, enabling network administrators to track user activity, session statistics, and billing data. This port complements RADIUS authentication (usually on port 1812 or alternatives), ensuring comprehensive management of network access and resource utilization..
The Remote Authentication Dial-In User Service (RADIUS) protocol is an AAA (Authentication, Authorization, and Accounting) protocol widely implemented for centralized network access management. While RADIUS authentication typically uses port 1812, port 1646 is a legacy alternative primarily dedicated to transmitting accounting information. This separation allows for streamlined management and better scalability within large network deployments.
RADIUS accounting messages provide administrators with session logs and usage metrics. These messages include data such as session time, data usage, user identities, and reasons for session termination. The protocol uses UDP by default; however, TCP support exists in some implementations to improve transmission reliability.
Cisco and Juniper Network devices historically default to port 1646 for this accounting functionality. With newer RFC standards (such as RFC 2866 and updated IANA port assignments), port 1813 superseded 1646 as the official accounting port. Nonetheless, many legacy and customized environments continue to leverage 1646, thus remaining relevant in network management scenarios.