VMware NSX Security

Disclaimer: This is a community-maintained open-source project and is not affiliated with, endorsed by, or sponsored by VMware, Inc. or Broadcom Inc. "VMware" and "NSX" are trademarks of Broadcom. Source code is publicly auditable at github.com/zw008/VMware-NSX-Security under the MIT license.

VMware NSX DFW microsegmentation and security — 20 MCP tools for distributed firewall, security groups, VM tags, Traceflow, and IDPS.

Domain-focused security skill for NSX-T / NSX 4.x Policy API. Companion skills: vmware-nsx (networking), vmware-aiops (VM lifecycle), vmware-monitor (read-only monitoring), vmware-avi (AVI/ALB/AKO), vmware-harden (compliance baselines). | vmware-pilot (workflow orchestration) | vmware-policy (audit/policy)

What This Skill Does

| Category | Tools | Count | |----------|-------|:-----:| | DFW Policy | list, get, create, update, delete, list rules | 6 | | DFW Rules | create, update, delete, get stats | 4 | | Security Groups | list, get, create, delete | 4 | | VM Tags | list VM tags, apply tag | 2 | | Traceflow | run trace, get result | 2 | | IDPS | list profiles, get status | 2 |

Total: 20 tools (10 read-only + 10 write)

Quick Install

uv tool install vmware-nsx-security
vmware-nsx-security doctor

When to Use This Skill

List, create, or modify DFW security policies and rules
Create security groups based on VM tags, IP ranges, or segment membership
Apply or list NSX tags on virtual machines
Run Traceflow to trace a packet path and diagnose drop reasons
Check IDPS profile configuration and engine status
Implement zero-trust microsegmentation between application tiers

Use companion skills for:

NSX segments, gateways, NAT, routing, IPAM → vmware-nsx
VM lifecycle, deployment, guest ops → vmware-aiops
vSphere inventory, health, alarms, events → vmware-monitor
Storage: iSCSI, vSAN, datastores → vmware-storage
Tanzu Kubernetes → vmware-vks
Load balancing, AVI/ALB, AKO, Ingress → vmware-avi

Related Skills — Skill Routing

| User Intent | Recommended Skill | |-------------|-------------------| | NSX security: DFW rules, security groups, IDS/IPS | vmware-nsx-security ← this skill | | NSX networking: segments, gateways, NAT, routing | vmware-nsx | | Read-only vSphere monitoring, alarms, events | vmware-monitor | | VM lifecycle, deployment, guest ops | vmware-aiops | | Storage: iSCSI, vSAN, datastores | vmware-storage | | Tanzu Kubernetes | vmware-vks | | Multi-step workflows with approval | vmware-pilot | | Compliance baselines (CIS / 等保 / PCI-DSS), drift detection, LLM remediation advisor | vmware-harden (uv tool install vmware-harden) | | Load balancer, AVI, ALB, AKO, Ingress | vmware-avi (uv tool install vmware-avi) | | Audit log query | vmware-policy (vmware-audit CLI) |

Common Workflows

Implement App-Tier Microsegmentation

Pre-flight (judgment — DFW changes can lock everyone out):

Default-allow first: the very first rule in any new policy must be ALLOW for management traffic (DNS, NTP, vCenter, SSH from jumphost). Without it, the moment you add a default-deny you blackhole your own access.
Tag inventory: confirm the VMs you intend to protect actually carry the tag (tag list <vm>). A group based on a non-existent tag matches zero VMs — the policy will appear "applied" but enforce nothing.
Category choice: Application for app-tier microseg (rules evaluated late, after Infrastructure rules pass through). Using Emergency for routine rules will starve real incident-response capacity.
Stateless? Default to stateful — NSX DFW is stateful and almost no rule should be stateless. Stateless = both directions must be explicitly allowed.
Always start with logging enabled on new rules; disable later once verified. Silent drops are the worst kind of bug.

Steps:

Tag the VMs first (see workflow below) — empty groups = no enforcement
group create web-vms --tag-scope tier --tag-value web (and app-vms)
policy create app-microseg --category Application
Add rules in order: ALLOW management → ALLOW intra-tier → ALLOW web→app on app-port → DROP any-any with logging
Verify with traceflow (see below) before enabling default-deny

Apply NSX Tags to VMs

Judgment: tags drive group membership which drives DFW enforcement. A misspelled tag silently excludes a VM from protection. Always re-list after applying.

tag list my-web-vm-01 → record the VM external ID, also see what tags already exist (avoid duplicates / typo collisions)
tag apply <vm-external-id> --scope tier --value web
Verify: tag list my-web-vm-01 again → confirm the new tag is present AND no unexpected ones

Trace a Packet with Traceflow

Judgment: traceflow is your verification mechanism for any DFW change. Run it before enabling deny rules and after every rule modification. Don't trust "looks right in the UI."

Get source VM's logical port ID via vmware-nsx troubleshoot vm-segment
traceflow run <lport-id> --src-ip <src> --dst-ip <dst> --proto TCP --dst-port <port>
Inspect the DFW hit chain: which rule matched, ALLOW or DROP, and at which transport node
Common failure: rule matches at category Application but is shadowed by an earlier DROP at category Environment — read the trace top-to-bottom, not just the final verdict

Check DFW Policy Hit Counts

vmware-nsx-security policy list
vmware-nsx-security rule list <policy-id>
vmware-nsx-security rule stats <policy-id> <rule-id>

Multi-Target Operations

All commands accept --target <name> to operate against a specific NSX Manager:

# Default target
vmware-nsx-security policy list

# Specific target
vmware-nsx-security policy list --target nsx-prod
vmware-nsx-security group list --target nsx-lab

Usage Mode

| Scenario | Recommended | Why | |----------|:-----------:|-----| | Local/small models (Ollama, Qwen) | CLI | ~2K tokens vs ~8K for MCP | | Cloud models (Claude, GPT-4o) | Either | MCP gives structured JSON I/O | | Automated pipelines | MCP | Type-safe parameters, structured output |

MCP Tools (20 — 10 read, 10 write)

All MCP tools accept an optional target parameter.

| Category | Tool | Type | Description | |----------|------|:----:|-------------| | DFW Policy | list_dfw_policies | Read | List all DFW security policies with category, sequence, and rule count | | | get_dfw_policy | Read | Get policy details: category, stateful, locked, scope, tags | | | create_dfw_policy | Write | Create a new DFW policy with category and sequence number | | | update_dfw_policy | Write | Partial update: display_name, description, sequence_number, stateful | | | delete_dfw_policy | Write | Delete policy — refuses if active rules exist | | | list_dfw_rules | Read | List rules in a policy: action, sources, destinations, services | | DFW Rules | create_dfw_rule | Write | Create rule with sources/destinations/services/action/scope | | | update_dfw_rule | Write | Partial update rule fields | | | delete_dfw_rule | Write | Delete a rule from a policy | | | get_dfw_rule_stats | Read | Get packet/byte hit counts for a rule | | Security Groups | list_groups | Read | List all security groups with expression count | | | get_group | Read | Get group details: expression criteria + up to 50 effective VM members | | | create_group | Write | Create group with tag/IP/segment membership criteria | | | delete_group | Write | Delete group — refuses if referenced by DFW rules | | VM Tags | list_vm_tags | Read | List NSX tags on a VM by display name | | | apply_vm_tag | Write | Apply a scope/value tag to a VM (additive, preserves existing tags) | | Traceflow | run_traceflow | Write | Inject probe packet and return hop-by-hop observations | | | get_traceflow_result | Read | Check status/observations of an existing traceflow | | IDPS | list_idps_profiles | Read | List IDPS profiles with severity and criteria | | | get_idps_status | Read | Get IDPS engine status: enabled/disabled, signature version, per-node counts |

CLI Quick Reference

# DFW Policy
vmware-nsx-security policy list [--target <name>]
vmware-nsx-security policy get <policy-id>
vmware-nsx-security policy create <id> --name "Display Name" --category Application [--dry-run]
vmware-nsx-security policy delete <id> [--dry-run]

# DFW Rules
vmware-nsx-security rule list <policy-id>
vmware-nsx-security rule stats <policy-id> <rule-id>
vmware-nsx-security rule delete <policy-id> <rule-id> [--dry-run]

# Security Groups
vmware-nsx-security group list
vmware-nsx-security group get <group-id>
vmware-nsx-security group delete <group-id> [--dry-run]

# Tags
vmware-nsx-security tag list <vm-display-name>
vmware-nsx-security tag apply <vm-external-id> --scope env --value production [--dry-run]

# Traceflow
vmware-nsx-security traceflow run <lport-id> --src-ip &lt;src-ip&gt; --dst-ip &lt;dst-ip&gt;

# IDPS
vmware-nsx-security idps profiles
vmware-nsx-security idps status

# Diagnostics
vmware-nsx-security doctor [--skip-auth]

Troubleshooting

"Cannot delete policy — active rules exist"

delete_dfw_policy checks for active rules before deleting. Use vmware-nsx-security rule list <policy-id> to see which rules need to be removed first. Then delete each rule individually before retrying the policy deletion.

"Cannot delete group — referenced by DFW rules"

delete_group scans all policies for rules that reference the group in source_groups or destination_groups. Remove the group from those rules first (via update_dfw_rule replacing the group path with 'ANY' or another group), then retry.

"No virtual machine found with display_name"

list_vm_tags looks up VMs by display name via the NSX fabric API. Common causes:

Display name mismatch — the name in NSX Manager may differ from vCenter. Check vmware-monitor vm list for the exact NSX fabric display name.
VM not registered — newly deployed VMs may take a minute to appear in the NSX fabric.
Multiple VMs with the same name — use apply_vm_tag with the specific external_id.

Traceflow returns empty observations

Verify the src_lport_id is the correct logical port attachment UUID — not the segment port path. Get it from vmware-nsx troubleshoot vm-segment <vm>.
The source VM must be powered on and connected to an NSX overlay segment.
If the VM is on a VLAN-backed segment, Traceflow is not supported.
NSX Manager requires the transport node hosting the source VM to be reachable. Check vmware-nsx health transport-nodes.

DFW rule stats show zero hits

A newly created rule will have zero hit counts until traffic matches it. If expected traffic still shows zero:

Confirm the rule is not disabled (disabled: false in list_dfw_rules output).
Check that source/destination group membership is correct using get_group.
Verify rule sequence number — a lower-sequence rule with ALLOW/DROP may be matching first.

"Password not found" error

Password variable convention: VMWARE_NSX_SECURITY_<TARGET_UPPER>_PASSWORD where hyphens are replaced by underscores. For target nsx-prod: VMWARE_NSX_SECURITY_NSX_PROD_PASSWORD. Check ~/.vmware-nsx-security/.env.

`invalid peer certificate: UnknownIssuer` (uvx)

Corporate TLS proxy not trusted by uv's bundled cert store. Use the v1.5.15+ single-command form vmware-nsx-security mcp (no PyPI re-resolve), or export UV_NATIVE_TLS=true to make uv use the system cert store.

Safety

Audit logging: All write operations logged to ~/.vmware/audit.db (SQLite WAL, via vmware-policy) with timestamp, user, target, operation, parameters, and result
Dependency checks: delete_dfw_policy checks for active rules; delete_group checks for DFW rule references — prevents accidental cascade failures
Input validation: All IDs validated against safe character set (alphanumerics, hyphens, underscores, dots); all text fields sanitized to strip control characters
Dry-run mode: CLI write commands support --dry-run to preview API calls without executing
Double confirmation: CLI destructive operations (delete) require two separate confirmation prompts
Credential safety: Passwords loaded only from environment variables (.env file), never from config.yaml
No networking changes: Cannot modify segments, gateways, NAT, or routing — that scope belongs to vmware-nsx
Prompt injection defense: All API-sourced strings passed through _sanitize() before inclusion in tool output

Setup

uv tool install vmware-nsx-security
mkdir -p ~/.vmware-nsx-security
cp config.example.yaml ~/.vmware-nsx-security/config.yaml
# Edit config.yaml with your NSX Manager targets

# Add to ~/.vmware-nsx-security/.env (create if missing, chmod 600):
# VMWARE_NSX_SECURITY_NSX_PROD_PASSWORD=<your-password>
chmod 600 ~/.vmware-nsx-security/.env

vmware-nsx-security doctor

All tools are automatically audited via vmware-policy. Audit logs: vmware-audit log --last 20

Full setup guide: see references/setup-guide.md

Architecture

User (natural language)
  |
AI Agent (Claude Code / Goose / Cursor)
  | reads SKILL.md
vmware-nsx-security CLI or MCP server (stdio transport)
  | NSX Policy API (REST/JSON over HTTPS)
NSX Manager
  |
DFW Policies / Rules / Security Groups / Tags / IDPS

The MCP server uses stdio transport (local only, no network listener). All connections to NSX Manager use HTTPS on port 443.

Audit & Safety

All operations are automatically audited via vmware-policy (@vmware_tool decorator):

Every tool call logged to ~/.vmware/audit.db (SQLite, framework-agnostic)
Policy rules enforced via ~/.vmware/rules.yaml (deny rules, maintenance windows, risk levels)
Risk classification: each tool tagged as low/medium/high/critical
View recent operations: vmware-audit log --last 20
View denied operations: vmware-audit log --status denied

vmware-policy is automatically installed as a dependency — no manual setup needed.

License

MIT — github.com/zw008/VMware-NSX-Security