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+# RADIUS Authentication Test Plan
+
+## Table of Contents
+- [RADIUS Authentication Test Plan](#radius-authentication-test-plan)
+  - [Table of Contents](#table-of-contents)
+  - [1 Overview](#1-overview)
+  - [2 Scope](#2-scope)
+  - [3 Test Setup](#3-test-setup)
+    - [3.1 Test Environment](#31-test-environment)
+    - [3.2 RADIUS Server Configuration](#32-radius-server-configuration)
+  - [4 Test Cases](#4-test-cases)
+    - [4.1 User Authentication Tests](#41-user-authentication-tests)
+    - [4.2 Command Authorization](#42-command-authorization)
+    - [4.3 Authentication Fallback](#43-authentication-fallback)
+    - [4.4 Error Handling](#44-error-handling)
+    - [4.5 Source IP Configuration](#45-source-ip-configuration)
+    - [4.6 Management VRF](#46-management-vrf)
+    - [4.7 IPv6 RADIUS Server Support](#47-ipv6-radius-server-support)
+  - [5 Implementation Details](#5-implementation-details)
+    - [5.1 Test Framework](#51-test-framework)
+    - [5.2 Key Utilities](#52-key-utilities)
+    - [5.3 Test Configuration](#53-test-configuration)
+  - [6 Expected Results](#6-expected-results)
+
+## 1 Overview
+
+This document outlines the test plan for validating RADIUS (Remote Authentication Dial-In User Service) authentication functionality in SONiC. The tests verify the proper configuration, operation, and integration of RADIUS authentication services with SONiC devices.
+
+## 2 Scope
+
+The test plan covers the following aspects of RADIUS authentication:
+- RADIUS server configuration and management
+- User authentication and authorization
+- Error handling and fallback mechanisms
+- Integration with SONiC authentication system
+
+Key components tested:
+- FreeRADIUS server setup and configuration
+- RADIUS client configuration on SONiC
+- User credentials management
+- Network connectivity between RADIUS client and server
+
+## 3 Test Setup
+
+### 3.1 Test Environment
+
+The test environment consists of:
+- SONiC Device Under Test (DUT)
+- PTF (Packet Test Framework) host running FreeRADIUS server
+- Test credentials defined in `radius_creds.yaml`
+- Network connectivity between DUT and RADIUS server
+
+Required packages and services:
+- FreeRADIUS server package
+- Configuration templates:
+  * `clients.conf.j2` - RADIUS client configuration
+  * `users.j2` - User authentication database
+
+### 3.2 RADIUS Server Configuration
+
+The RADIUS server is configured with:
+- Server IP address and authentication port (default: 1812)
+- Shared secret for client authentication
+- User database with test credentials
+- Client configuration for DUT access
+
+Configuration files:
+```
+/etc/freeradius/3.0/
+├── clients.conf          # Client configuration
+└── mods-config/
+    └── files/
+        └── authorize     # User database
+```
+
+## 4 Test Cases
+
+### 4.1 User Authentication Tests
+
+**Test Case 1: Read-Write User Authentication (`test_radius_rw_user`)**
+- Verify authentication of read-write user
+- Test user group membership using `cat /etc/group`
+- Verify RADIUS statistics:
+  * Access-Accept counter increments
+  * Access-Reject counter remains unchanged
+
+**Test Case 2: Read-Only User Authentication (`test_radius_ro_user`)**
+- Verify authentication of read-only user
+- Test user group membership using `cat /etc/passwd`
+- Verify RADIUS statistics:
+  * Access-Accept counter increments
+  * Access-Reject counter remains unchanged
+
+### 4.2 Command Authorization
+
+**Test Case 3: Command Authorization (`test_radius_command_auth`)**
+- Test read-only user access to allowed commands:
+  * show version
+  * show interface status
+  * show lldp table
+  * show ip bgp summary
+  * show ip route
+  * sudo cat /var/log/syslog
+- Test read-only user access to restricted commands:
+  * sudo config -h
+  * sudo cat /var/log/auth.log
+- Verify proper authorization enforcement
+
+### 4.3 Authentication Fallback
+
+**Test Case 4: Local Authentication Fallback (`test_radius_fallback`)**
+- Setup local user with password
+- Test authentication with local credentials
+- Verify RADIUS statistics:
+  * Access-Reject counter increments
+- Confirm fallback to local authentication works
+
+### 4.4 Error Handling
+
+**Test Case 5: Failed Authentication (`test_radius_failed_auth`)**
+- Test authentication with invalid credentials
+- Verify authentication failure
+- Verify RADIUS statistics:
+  * Access-Reject counter increments
+
+### 4.5 Source IP Configuration
+
+**Test Case 6: Source IP Feature (`test_radius_source_ip`)**
+- Configure RADIUS source interface
+- Capture RADIUS packets using tcpdump
+- Verify RADIUS packets use correct source IP
+- Skip test if no routed interfaces are available
+
+### 4.6 Management VRF
+
+**Test Case 7: RADIUS with Management VRF (`test_radius_mgmt_vrf`)**
+- Enable management VRF on DUT
+- Verify RADIUS server reachability through mgmt VRF
+- Test read-write user authentication:
+  * Verify successful authentication
+  * Check user group membership
+  * Verify RADIUS statistics:
+    - Access-Accept counter increments
+    - Access-Reject counter remains unchanged
+- Test read-only user authentication:
+  * Verify successful authentication
+  * Check user group membership
+  * Verify RADIUS statistics:
+    - Access-Accept counter increments
+    - Access-Reject counter remains unchanged
+- Clean up:
+  * Remove management VRF
+  * Verify SSH accessibility after VRF removal
+
+### 4.7 IPv6 RADIUS Server Support
+
+**Test Case 8: IPv6-only RADIUS Authentication (`test_radius_ipv6_only`)**
+- Configure RADIUS server with IPv6 address only
+- Verify RADIUS server configuration:
+  * Check IPv6 address is properly configured
+  * Verify connectivity to RADIUS server over IPv6
+- Test read-write user authentication:
+  * Verify successful authentication
+  * Check user group membership
+  * Verify RADIUS statistics:
+    - Access-Accept counter increments
+    - Access-Reject counter remains unchanged
+- Test read-only user authentication:
+  * Verify successful authentication
+  * Check user group membership
+  * Verify RADIUS statistics:
+    - Access-Accept counter increments
+    - Access-Reject counter remains unchanged
+- Test command authorization for both user types
+- Test authentication failure with invalid credentials
+- Verify RADIUS packets use correct IPv6 source and destination addresses
+- Clean up:
+  * Remove IPv6 RADIUS server configuration
+  * Restore IPv4 RADIUS server configuration
+
+**Test Case 9: Dual-Stack RADIUS Server Failover (`test_radius_ipv6_failover`)**
+- Configure RADIUS server with both IPv4 and IPv6 addresses
+- Set priority to prefer IPv6 server
+- Verify primary (IPv6) server authentication works
+- Disable IPv6 connectivity to RADIUS server
+- Verify failover to IPv4 RADIUS server:
+  * Confirm authentication still succeeds
+  * Verify RADIUS statistics show IPv4 server is being used
+- Re-enable IPv6 connectivity
+- Verify system fails back to IPv6 RADIUS server
+- Clean up:
+  * Restore original RADIUS server configuration
+
+## 5 Implementation Details
+
+### 5.1 Test Framework
+- Python pytest framework
+- Test fixtures for setup and teardown:
+  * `radius_creds`: Loads test credentials
+  * `setup_radius_server`: Configures FreeRADIUS
+  * `setup_radius_client`: Configures DUT
+
+### 5.2 Key Utilities
+- `ssh_remote_run`: Execute commands via SSH
+- `check_radius_stats`: Monitor RADIUS counters
+- `verify_radius_capture`: Analyze packet captures
+- `check_group_output`: Verify user group membership
+
+### 5.3 Test Configuration
+- Credentials stored in `radius_creds.yaml`
+- Server configuration via Jinja2 templates
+- DUT configuration using SONiC CLI
+
+## 6 Expected Results
+
+All test cases should:
+- Complete successfully without errors
+- Verify proper authentication behavior
+- Handle error conditions gracefully
+- Clean up configurations after completion
+
+Test failures should provide:
+- Clear error messages
+- Relevant log information
+- RADIUS statistics for debugging