get_network_instances

THE RISK

Low Risk

Why get_network_instances needs a policy

This tool queries network device state to return a list of virtual routing and forwarding (VRF) instances or similar logical network partitions. It performs a read-only operation with no side effects, no data modification, no code execution, and no destructive capabilities. Misuse by an AI agent would only expose network topology information, presenting minimal risk.

From the tool's definition Tool name is 'get_network_instances' with description 'Retrieve a list of network instances (e.g., VRFs)'. The verb 'Retrieve' and 'get_' prefix indicate data retrieval with no modification or execution of commands.

Documented attack patterns abuse exactly the kind of access get_network_instances gives an agent:

POLICY

How to control get_network_instances

PolicyLayer is an MCP gateway — it sits between your AI agents and Nornir MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for get_network_instances:

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "get_network_instances": {}
  }
}

get_network_instances is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.

Create a free account and register Nornir MCP Server — nothing to install.
Add this policy — paste it, or build it visually.
Point your MCP client (Claude, Cursor, anything) at your gateway URL.

CAP THIS TOOL →

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EXPLORE

Related tools and policies

More Nornir MCP Server tools

Execute traceroute Execute the traceroute command from the device to the specified destination. Execute send_command Send a validated read-only command or list of commands to the device. Read get_arp_table Get the device's ARP (Address Resolution Protocol) table. Read get_bgp_config Retrieve BGP configuration from the device. Read get_bgp_neighbors Get a summary of BGP (Border Gateway Protocol) neighbors. Read get_bgp_neighbors_detail Obtain a detailed view of all BGP neighbors. Read get_config Use NAPALM to retrieve device configurations (running, startup, or candidate). Read get_facts Retrieve high-level facts and information about the device (e.g., vendor, model, serial nu

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Go deeper

The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Data exfiltration → How read access becomes an exfiltration channel when chained with untrusted content.
MCP token cost → What connecting this server costs in context-window tokens on every request.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about get_network_instances

What does the get_network_instances tool do? +

Retrieve a list of network instances (e.g., VRFs). It is categorised as a Read tool in the Nornir MCP Server MCP Server, which means it retrieves data without modifying state.

How do I enforce a policy on get_network_instances? +

Register the Nornir MCP Server MCP server in PolicyLayer and add a rule for get_network_instances: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches Nornir MCP Server. Nothing to install.

What risk level is get_network_instances? +

get_network_instances is a Read tool with low risk. Read-only tools are generally safe to allow by default.

Can I rate-limit get_network_instances? +

Yes. Add a rate_limit block to the get_network_instances rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.

How do I block get_network_instances completely? +

Set action: deny in the PolicyLayer policy for get_network_instances. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.

What MCP server provides get_network_instances? +

get_network_instances is provided by the Nornir MCP Server MCP server (yhvh-chen/nornir_mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Nornir MCP Server tool call.

Start from Nornir MCP Server, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.

CHECK YOUR STACK →