Junos

A Model Context Protocol (MCP) server for Juniper Junos devices that enables LLM interactions with network equipment.

Table of Contents

• junos-mcp-server
  • Table of Contents
  • Important Security Notice
    • Security Requirements
    • Security Best Practices
  • Important Configuration Notice
  • Getting Started
    • Running with uv
  • Start Junos MCP Server
  • Configuration
    • Config for Claude Desktop (stdio transport)
    • Config for Claude Desktop (using uv)
    • Config for Claude Desktop (Docker container)
  • Docker Usage
    • Build Docker Container
    • Running with Default Settings
    • Overriding Default Arguments
  • Junos Device Configuration
  • VSCode + GitHub Copilot Integration
    • Start Your Server
    • Point to This URL in Your VSCode Config
  • Authentication for MCP Server Access
    • Authentication Behavior
    • Token Management
      • Generate a New Token
      • List All Tokens
      • Show Token Value (Recovery)
      • Revoke a Token
    • Server Authentication Status
    • Client Configuration with Authentication
      • VSCode Configuration with Token
      • Testing with curl
      • Docker with Authentication
    • Security Best Practices
    • Token File Format
  • GuardRails for Config Commit
  • GuardRails for Executing Operational Commands
  • Using MCP Server with Juniper Cloud-Native Router (JCNR)
  • Developer Guide
    • Architecture Overview
    • How Tools Work
    • Adding a New Tool
      • Step 1: Create a Handler Function
      • Step 2: Register the Handler
      • Step 3: Define Tool Metadata
    • Example: Creating a BGP Neighbors Tool
    • Best Practices for Tool Development
    • Using PyEZ for Advanced Operations
    • Testing Your Tools
    • Debugging Tips

Important Security Notice

Warning: This server enables LLM access to your network infrastructure. Please review these security considerations carefully.

Security Requirements

• Corporate Policy Compliance: Only use this server if your company's policy allows sending data of Junos devices to LLM services.

• Server Security: Always secure your Junos MCP server before deployment in production environments.

• Authentication: Do not use password authentication for production deployments. We strongly recommend using SSH key-based authentication for enhanced security.

• Deployment Strategy: Until your MCP server is properly secured, only deploy locally for testing purposes. Do not deploy remote servers in production without proper security measures.

Security Best Practices

• Use SSH key authentication instead of passwords
• Implement proper network access controls
• Monitor and log all MCP server activities
• Regular security audits and updates
• Follow your organization's security policies

Important Configuration Notice

Warning: The Junos MCP server supports configuration changes, but please ensure you only use this functionality when you want LLM-generated configurations to be loaded and committed on your Junos router.

Always review the configuration being generated by the LLM and only allow tool execution if it's the correct configuration for your use case.

Getting Started

Get the code.

git clone https://github.com/Juniper/junos-mcp-server.git
cd junos-mcp-server
pip install -r requirements.txt

Running with uv

If you're using uv, you can run the server directly:

uv run python jmcp.py -f devices.json -t stdio

Start Junos MCP Server

python3.11 jmcp.py --help
Junos MCP Server

options:
  -h, --help            show this help message and exit
  -f DEVICE_MAPPING, --device-mapping DEVICE_MAPPING
                        the name of the JSON file containing the device mapping
  -H HOST, --host HOST  Junos MCP Server host
  -t TRANSPORT, --transport TRANSPORT
                        Junos MCP Server transport
  -p PORT, --port PORT  Junos MCP Server port

Junos MCP server supports both streamable-http and stdio transport. Do not use --host with stdio transport.

Environment Variables

• JUNOS_TIMEOUT: Command timeout in seconds for Junos CLI operations.
• JMCP_POOL_IDLE_TIMEOUT: Idle timeout in seconds for pooled SSH/NETCONF connections.
  • SSH sessions are reused across tool calls via a connection pool; a background cleanup thread (running once a minute) closes connections idle longer than this timeout.
  • Default: 300. Invalid values are logged and fall back to the default.

Configuration

Config for Claude Desktop (stdio transport)

{
  "mcpServers": {
    "jmcp": {
      "type": "stdio",
      "command": "python3",
      "args": ["jmcp.py", "-f", "devices.json", "-t", "stdio"]
    }
  }
}

Config for Claude Desktop (using uv)

{
  "mcpServers": {
    "jmcp": {
      "type": "stdio",
      "command": "uv",
      "args": ["run", "python", "jmcp.py", "-f", "devices.json", "-t", "stdio"]
    }
  }
}

Note: Please provide absolute path for jmcp.py and devices.json file.

Config for Claude Desktop (Docker container)

{
  "mcpServers": {
    "jmcp": {
      "type": "stdio",
      "command": "/usr/local/bin/docker",
      "args": [
        "run",
        "--rm",
        "-i",
        "-v",
        "devices.json:/app/config/devices.json",
        "-v",
        "vsrx_keypair.pem:/app/config/vsrx_keypair.pem",
        "junos-mcp-server:latest"
      ]
    }
  }
}

Docker Usage

Build Docker Container

docker build -t junos-mcp-server:latest .

Running with Default Settings

By default, the Docker container runs with stdio transport:

docker run --rm -it -v /path/to/your/devices.json:/app/config/devices.json
junos-mcp-server:latest

This uses the default command: python jmcp.py -f /app/config/devices.json -t stdio

Overriding Default Arguments

You can override any arguments by specifying the full command:

For stdio transport:

docker run --rm -it -v /path/to/your/devices.json:/app/config/devices.json
junos-mcp-server:latest python jmcp.py -f /app/config/devices.json -t stdio

For streamable-http transport:

Security: the streamable-http transport refuses to start without a valid .tokens file. Generate one with python jmcp_token_manager.py generate --id <token-id> and mount it into the container as shown below. See Authentication for details, or pass --allow-unauthenticated-http for loopback-only local development.

docker run --rm -it \
  -v /path/to/your/devices.json:/app/config/devices.json \
  -v /path/to/.tokens:/app/.tokens \
  -p 30030:30030 \
  junos-mcp-server:latest \
  python jmcp.py -f /app/config/devices.json -t streamable-http -H 0.0.0.0

For streamable-http with custom port:

docker run --rm -it \
  -v /path/to/your/devices.json:/app/config/devices.json \
  -v /path/to/.tokens:/app/.tokens \
  -p 8080:8080 \
  junos-mcp-server:latest \
  python jmcp.py -f /app/config/devices.json -t streamable-http -p 8080 -H 0.0.0.0

Note:

• Always mount your device configuration file using -v /path/to/you/ devices.json:/app/config/devices.json
• For streamable-http transport, expose the port using -p host_port:container_port
• Mount any SSH private key files if using key-based authentication (e.g., -v /path/to/key.pem:/app/config/key.pem)

Build docker container for Junos MCP Server

docker build -t junos-mcp-server:latest .

Note: Mount your config file devices.json and mount any other files, in my case I am using pem file for ssh priv key authentication so I am also mounting vsrx_keypair.pem

Junos Device Configuration

Junos MCP server supports both password based auth as well as SSH key based authentication (See first 2 routers configs [router-1, router-2]).

{
    "router-1": {
        "ip": "ip-addr",
        "port": 22,
        "username": "user",
        "auth": {
            "type": "password",
            "password": "pwd"
        }
    },
    "router-2": {
        "ip": "ip-addr",
        "port": 22,
        "username": "user",
        "auth": {
            "type": "ssh_key",
            "private_key_path": "/path/to/private/key.pem"
        }
    },
    "router-3": {
        "ip": "ip-addr",
        "port": 22,
        "username": "user",
        "ssh_config": "~/.ssh/config_dc",
        "auth": {
            "type": "ssh_key",
            "private_key_path": "/path/to/private/key.pem"
        }
    },
    "router-4": {
        "ip": "ip-addr",
        "port": 22,
        "username": "user",
        "ssh_config": "/home/user/.ssh/config_jumphost",
        "auth": {
            "type": "password",
            "password": "pwd"
        }
    }
}

Junos MCP server also provides support for ProxyCommand. (See last 2 routers configs [router-3, router-4]), which enables you to access a target device through an intermediary host that supports netcat. This is useful when you can only log in to the target device through the intermediate host (jumphost).

This is an example of an SSH config file being used .ssh/config_jumphost:

# Jumphost VM Connection
Host jumphost-vm
  HostName 10.2.11.200
  User root
  # Used for MCP server
  IdentityFile /home/user/.ssh/id_rsa_claude
  IdentitiesOnly yes
  StrictHostKeyChecking no

# cRPD Devices (via jump host)
Host dt-crpd1 dtwin-crpd1 digital-twin-crpd1 clab-digital-twin-eop6-pe1
    HostName 172.20.20.11
    User claude
    IdentityFile c
    # ProxyJump jumphost-vm # Not working with JunOS MCP
    ProxyCommand ssh -l root jumphost-vm nc %h 22 2>/dev/null
    StrictHostKeyChecking no

Note #1: Port value should be an integer (typically 22 for SSH).

Note #2: IdentityFile recommendation use full path (e.g /home/user/.ssh /id_rsa_claude rather than ~/.ssh/id_rsa_claude).

VSCode + GitHub Copilot Integration

Start Your Server

python3.11 jmcp.py -f devices.json
[06/11/25 08:26:11] INFO     Starting MCP server 'jmcp-server' with transport
'streamable-http' on http://127.0.0.1:30030/mcp
INFO:     Started server process [33512]
INFO:     Waiting for application startup.
INFO:     Application startup complete.
INFO:     Uvicorn running on http://127.0.0.1:30030 (Press CTRL+C to quit)

Point to This URL in Your VSCode Config

{
    "mcp": {
        "servers": {
            "my-junos-mcp-server": {
                "url": "http://127.0.0.1:30030/mcp/"
            }
        }
    }
}

Note: You can use VSCode's Cmd+Shift+P to configure MCP server.

Authentication for MCP Server Access

The Junos MCP server supports token-based authentication for secure client access when using streamable-http transport. This prevents unauthorized access to your network infrastructure.

Authentication Behavior

• stdio transport (Claude Desktop): No authentication required - secure by design as it runs locally
• streamable-http transport (VSCode, web clients): Token-based authentication available

Token Management

The server includes a dedicated token management CLI tool: jmcp_token_manager.py

Generate a New Token

# Basic token generation
python jmcp_token_manager.py generate --id "vscode-dev"

# With description
python jmcp_token_manager.py generate --id "vscode-dev" --description "VSCode
development environment"

# Example output:
Generated new token:
  ID: vscode-dev
  Token: jmcp_a1b2c3d4e5f6g7h8i9j0k1l2m3n4o5p6q7r8
  Description: VSCode development environment

Save this token securely - it won't be shown again!

List All Tokens

python jmcp_token_manager.py list

# Example output:
ID                   Description                              Created
-------------------------------------------------------------------------------------
vscode-dev          VSCode development environment
2025-01-28T10:30:00Z
prod-client         Production client access
2025-01-28T09:15:00Z

Show Token Value (Recovery)

python jmcp_token_manager.py show --id "vscode-dev"

# Example output:
Token ID: vscode-dev
Token: jmcp_a1b2c3d4e5f6g7h8i9j0k1l2m3n4o5p6q7r8
Description: VSCode development environment
Created: 2025-01-28T10:30:00Z

Revoke a Token

python jmcp_token_manager.py revoke --id "vscode-dev"

# Example output:
Token 'vscode-dev' has been revoked

Server Authentication Status

For the streamable-http transport the server fails closed: it refuses to start unless a valid, non-empty .tokens file is present. The only way to start without tokens is the explicit --allow-unauthenticated-http flag, which is in turn restricted to loopback binds (127.0.0.1, ::1, localhost).

With tokens configured:

python jmcp.py -f devices.json -t streamable-http
INFO - Token-based authentication enabled
INFO - Clients must send 'Authorization: Bearer <token>' header
INFO - Use jmcp_token_manager.py to manage tokens
INFO - Streamable HTTP server started on http://127.0.0.1:30030

Without tokens configured (default - refuses to start):

python jmcp.py -f devices.json -t streamable-http
ERROR - Refusing to start streamable-http transport without authentication: .tokens file not found
ERROR - Generate a token with: python jmcp_token_manager.py generate --id <token-id>
ERROR - Or, for local development on loopback only, re-run with --allow-unauthenticated-http

Explicit unauthenticated mode (loopback only, development only):

python jmcp.py -f devices.json -t streamable-http --allow-unauthenticated-http
WARNING - *** Streamable HTTP authentication is DISABLED (--allow-unauthenticated-http). .tokens file not found. Server is open to any client that can reach 127.0.0.1:30030 and can commit configuration to mapped devices. Use only for local development. ***
INFO - Streamable HTTP server started on http://127.0.0.1:30030

Combining --allow-unauthenticated-http with a non-loopback bind (for example -H 0.0.0.0) is rejected at startup.

Client Configuration with Authentication

VSCode Configuration with Token

{
    "mcp": {
        "servers": {
            "my-junos-mcp-server": {
                "url": "http://127.0.0.1:30030/mcp/",
                "headers": {
                    "Authorization": "Bearer
                    jmcp_a1b2c3d4e5f6g7h8i9j0k1l2m3n4o5p6q7r8"
                }
            }
        }
    }
}

Testing with curl

# Test authentication with valid token
curl -X POST "http://127.0.0.1:30030/mcp/" \
  -H "Authorization: Bearer jmcp_a1b2c3d4e5f6g7h8i9j0k1l2m3n4o5p6q7r8" \
  -H "Content-Type: application/json" \
  -H "Accept: application/json, text/event-stream" \
  -d '{"jsonrpc":"2.0","id":1,"method":"tools/list","params":{}}'

# Test without token (should fail with 401)
curl -X POST "http://127.0.0.1:30030/mcp/" \
  -H "Content-Type: application/json" \
  -H "Accept: application/json, text/event-stream" \
  -d '{"jsonrpc":"2.0","id":1,"method":"tools/list","params":{}}'

Note: MCP streamable-http requires the Accept: application/json, tex /event-stream header.

Docker with Authentication

When using Docker, mount the .tokens file to enable authentication:

# Generate token first (outside container)
python jmcp_token_manager.py generate --id "docker-client"

# Run container with token file mounted
docker run --rm -it \
  -v /path/to/devices.json:/app/config/devices.json \
  -v /path/to/.tokens:/app/.tokens \
  -p 30030:30030 \
  junos-mcp-server:latest \
  python jmcp.py -f /app/config/devices.json -t streamable-http -H 0.0.0.0

Security Best Practices

1. Token Security:

   • Store tokens securely (password managers, environment variables)
   • Use descriptive token IDs for easy management
   • Regularly rotate tokens by revoking old ones and generating new ones
   • Never commit tokens to version control

2. Access Control:

   • Generate separate tokens for different clients/environments
   • Revoke tokens immediately when no longer needed
   • Monitor server logs for unauthorized access attempts

3. Network Security:

   • Run streamable-http server behind reverse proxy with HTTPS in production
   • Use firewall rules to restrict access to MCP server port
   • Consider VPN access for remote clients

Token File Format

The .tokens file stores tokens in JSON format:

{
  "vscode-dev": {
    "token": "jmcp_a1b2c3d4e5f6g7h8i9j0k1l2m3n4o5p6q7r8",
    "description": "VSCode development environment",
    "created": "2025-01-28T10:30:00Z"
  },
  "prod-client": {
    "token": "jmcp_x9y8z7w6v5u4t3s2r1q0p9o8n7m6l5k4j3i2",
    "description": "Production client access",
    "created": "2025-01-28T09:15:00Z"
  }
}

Important: Keep this file secure and don't commit it to version control.

GuardRails for Config Commit

The load_and_commit_config tool now includes a pre-commit guardrail check that validates the submitted candidate configuration against patterns in block.cfg before any device commit actions are attempted.

How it works

• Each non-comment line in block.cfg is treated as a blocked pattern.
• Pattern matching is done against normalized config lines from the submitted config_text.
• Patterns support regex tokens (for example to match dynamic usernames).
• If any line matches, the request is rejected and no configuration is loaded or committed.

Example block.cfg

# Blocked configuration prefixes/patterns for load_and_commit_config
set system root-authentication
set system login user ([^ ]+) authentication

This protects common high-risk configuration areas (for example, root authentication or unmanaged local user credential changes) from being committed by automation.

GuardRails for Executing Operational Commands

The execute_junos_command and execute_junos_command_batch tools now include command guardrails using block.cmd.

How it works

• Each non-comment line in block.cmd is treated as a regex command pattern.
• Submitted commands are normalized and checked before execution.
• If a command matches a blocked pattern, execution is rejected.
• For batch execution, the blocked command is rejected before dispatching to routers.

Example block.cmd

# Blocked operational command prefixes/patterns for execute_junos_command
request system reboot
request system halt
request system power-cycle
request system power-off
request system zeroize

This blocks disruptive commands (reboot/power/zeroize class actions) while still allowing read-only operational show commands.

Using MCP Server with Juniper Cloud-Native Router (JCNR)

JCNR is a cloud native router that runs on various cloud environments. One can use this MCP server with JCNR as well by following the steps given below. Please refer to JCNR documentation for more details on configuration.

• Configure SSH access in JCNR on a desired port other than 22. This is required because, JCNR runs as a container on shared operating system. Running SSH on default port is not recommended. By default SSH is enabled on port 24. But, it is preferred to change this to desired port depending on your networking needs.
• Enable authentication method for SSH. JCNR supports SSH key and password based authentications.
• Enable Netconf over SSH. This is enabled by default.

set system services netconf ssh
set system services ssh port 3030
set system services ssh root-login allow
set system root-authentication encrypted-password
"$6$3vvMI$RNemhmu9izWXzO46msh38frIg4VoeFNJWJZugxgnU.NQso3OQ00QWOIZmzNePD.MWjDOD
BBEYut/W7kfADdV." (or)
set system root-authentication load-key-file <public key>

Developer Guide

This section explains the architecture of the Junos MCP server and how to extend it with new tools.

Architecture Overview

The Junos MCP server uses the Model Context Protocol (MCP) to enable LLMs to interact with Juniper network devices. The server architecture consists of:

1. MCP Server Core (jmcp.py): Handles MCP protocol communication
2. Tool Handlers: Individual functions that implement specific network operations
3. Tool Registry: Maps tool names to their handler functions
4. Transport Layer: Supports stdio (Claude Desktop) and streamable-http (VSCode)

How Tools Work

Each tool in the MCP server follows this flow:

Adding a New Tool

Adding a new tool is a simple 3-step process:

Step 1: Create a Handler Function

Create an async handler function in jmcp.py (before the TOOL_HANDLERS dictionary):

async def handle_my_new_tool(arguments: dict) -> list[types.ContentBlock]:
    """Handler for my_new_tool - describe what it does"""
    # Extract arguments
    router_name = arguments.get("router_name", "")
    my_param = arguments.get("my_param", "default_value")

    # Validate router exists
    if router_name not in devices:
        result = f"Router {router_name} not found in the device mapping."
    else:
        # Your tool logic here
        log.debug(f"Executing my_new_tool on router {router_name}")
        result = _run_junos_cli_command(router_name, f"show {my_param}")

    return [types.TextContent(type="text", text=result)]

Step 2: Register the Handler

Add your handler to the TOOL_HANDLERS dictionary (around line 330):

TOOL_HANDLERS = {
    "execute_junos_command": handle_execute_junos_command,
    "get_junos_config": handle_get_junos_config,
    "junos_config_diff": handle_junos_config_diff,
    "gather_device_facts": handle_gather_device_facts,
    "get_router_list": handle_get_router_list,
    "load_and_commit_config": handle_load_and_commit_config,
    "my_new_tool": handle_my_new_tool,    # Add your tool here
}

Step 3: Define Tool Metadata

Add the tool definition to the list_tools() method (around line 410):

types.Tool(
    name="my_new_tool",
    description="Brief description of what your tool does",
    inputSchema={
        "type": "object",
        "properties": {
            "router_name": {"type": "string", "description": "The name of the
            router"},
            "my_param": {"type": "string", "description": "Description of
            parameter"}
        },
        "required": ["router_name"]  # List required parameters
    }
)

Example: Creating a BGP Neighbors Tool

Here's a complete example of adding a tool to show BGP neighbors:

# Step 1: Handler function
async def handle_show_bgp_neighbors(arguments: dict) -> list[types.ContentBloc
]:
    """Handler for show_bgp_neighbors tool"""
    router_name = arguments.get("router_name", "")
    neighbor_address = arguments.get("neighbor_address", "")

    if router_name not in devices:
        result = f"Router {router_name} not found in the device mapping."
    else:
        log.debug(f"Getting BGP neighbors from router {router_name}")
        if neighbor_address:
            cmd = f"show bgp neighbor {neighbor_address}"
        else:
            cmd = "show bgp summary"
        result = _run_junos_cli_command(router_name, cmd)

    return [types.TextContent(type="text", text=result)]

# Step 2: Add to TOOL_HANDLERS
TOOL_HANDLERS = {
    # ... existing tools ...
    "show_bgp_neighbors": handle_show_bgp_neighbors,
}

# Step 3: Add to list_tools()
types.Tool(
    name="show_bgp_neighbors",
    description="Show BGP neighbor information",
    inputSchema={
        "type": "object",
        "properties": {
            "router_name": {"type": "string", "description": "The name of the
            router"},
            "neighbor_address": {"type": "string", "description": "Optional:
            specific neighbor IP"}
        },
        "required": ["router_name"]
    }
)

Best Practices for Tool Development

1. Error Handling: Always handle connection errors and invalid inputs gracefully
2. Logging: Use the global log logger for debugging
3. Validation: Check if router exists before attempting operations
4. Documentation: Write clear descriptions for tools and parameters
5. Timeouts: Support configurable timeouts for long-running operations
6. Return Format: Always return list[types.ContentBlock] with text content
7. Context Parameter: Use the context: Context parameter to send progress and log messages to the client

Using PyEZ for Advanced Operations

For operations beyond CLI commands, use PyEZ directly:

from jnpr.junos import Device
from jnpr.junos.utils.config import Config

# Example: Using PyEZ tables
async def handle_get_interfaces(arguments: dict) -> list[types.ContentBlock]:
    router_name = arguments.get("router_name", "")

    if router_name not in devices:
        result = f"Router {router_name} not found in the device mapping."
    else:
        device_info = devices[router_name]
        try:
            connect_params = prepare_connection_params(device_info, router_name)
            with Device(**connect_params) as junos_device:
                # Use PyEZ tables or other utilities
                interfaces = junos_device.rpc.get_interface_information()
                # Process interfaces...
                result = "Interface information..."
        except Exception as e:
            result = f"Error: {e}"

    return [types.TextContent(type="text", text=result)]

Testing Your Tools

1. Unit Testing: Test handler functions with mock arguments
2. Integration Testing: Test with actual Junos devices or vSRX
3. Error Cases: Test with invalid routers, network failures, etc.

Example test:

# Test the handler directly
result = await handle_my_new_tool({
    "router_name": "router-1",
    "my_param": "test"
})
print(result[0].text)

Debugging Tips

1. Enable debug logging to see detailed execution:

 logging.basicConfig(level=logging.DEBUG)

2. Use the stdio transport for easier debugging:

 python jmcp.py -f devices.json -t stdio

3. Test individual commands manually:

 result = _run_junos_cli_command("router-1", "show version")
 print(result)