VMware NSX

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/vmware-skills/VMware-NSX under the MIT license.

VMware NSX networking management — 33 MCP tools for segments, gateways, NAT, routing, and IPAM.

Domain-focused networking skill for NSX-T / NSX 4.x Policy API. Companion skills: vmware-nsx-security (DFW/firewall), vmware-aiops (VM lifecycle), vmware-monitor (read-only monitoring), vmware-storage (iSCSI/vSAN), vmware-vks (Tanzu Kubernetes), vmware-aria (metrics/alerts/capacity), vmware-avi (AVI/ALB/AKO), vmware-harden (compliance baselines). | vmware-pilot (workflow orchestration) | vmware-policy (audit/policy)

What This Skill Does

Total: 33 tools (20 read-only + 13 write)

Quick Install

uv tool install vmware-nsx-mgmt==1.15.1
vmware-nsx init      # guided setup: writes config + .env (chmod 600, password grep-safe), then verifies
vmware-nsx doctor

When to Use This Skill

• List, create, or modify NSX segments (overlay / VLAN-backed)
• Create or manage Tier-0 / Tier-1 gateways
• Configure NAT rules (SNAT, DNAT, reflexive)
• View or add static routes, check BGP neighbors
• Manage IP pools and subnet allocations
• Check NSX alarms, transport node health, edge cluster status
• Find which segment a VM is connected to
• Troubleshoot logical port status

Use it only when the request is explicitly about NSX (NSX-T / NSX 4.x, NSX Manager). Writes only on request: call a create/update/delete tool, NAT/route/IP-pool change, or Tier-0 BGP change only when the user has explicitly asked for that specific change — never as a side step of a read, health check, or troubleshooting task. Diagnose with read tools first and propose the change instead.

Use companion skills for:

• Distributed firewall, security groups, DFW rules, IDS/IPS → vmware-nsx-security
• vSphere distributed port groups, host VMkernel adapters → vmware-aiops
• 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

Common Workflows

Create an App Network (Segment + T1 Gateway + NAT)

Pre-flight (judgment, not blind sequence):

• Subnet conflict check: scan inventory list-segments and networking list-ip-pools for any overlap with the proposed CIDR. Overlapping subnets cause asymmetric routing or silent blackholing — NSX will not warn you.
• Edge cluster capacity: confirm chosen --edge-cluster is healthy (inventory list-edge-clusters + health edge-cluster-status <id>) and not at SR (Service Router) limit. A fully-loaded edge cluster will accept the T1 creation but routing will fail.
• T0 uplink: the parent T0 must already be configured with BGP/static routes upstream — otherwise SNAT works internally but external traffic goes nowhere.
• NAT IP: --translated IP must be from a routable address pool announced by T0; using a random IP creates a half-working network.
• Always --dry-run first — once a segment is attached to running VMs, deleting it requires detaching every port.

Steps:

1. vmware-nsx gateway create-tier1 app-t1 --name app-t1 --edge-cluster <ec-path> --tier0 <t0-path> --dry-run → review, then run for real
2. vmware-nsx segment create app-web-seg --name app-web-seg --tz <tz-overlay-path> --subnet <gw-cidr>
3. vmware-nsx nat create-rule --tier1 app-t1 --rule-id snat-1 --action SNAT --source <private-cidr> --translated <pub-ip>
4. Verify end-to-end: inventory list-segments, networking list-nat-rules app-t1, AND test with a VM attached to the new segment
5. On failure: a connection error or HTTP error prints a single teaching line (e.g. 403 → check NSX role privileges; 404 → run the matching list command for the exact ID). Run vmware-nsx doctor to verify connectivity and credentials, fix, and re-run the failed step — earlier completed steps are idempotent PUTs and safe to re-apply.

Check Network Health

Judgment: don't just enumerate health endpoints — correlate them. The order below maps cause to symptom: if manager is down, transport nodes will look down too (false positive); fix top-down.

1. vmware-nsx health manager-status — if any manager node is DEGRADED or DOWN, stop here and resolve before trusting downstream signals
2. vmware-nsx inventory list-transport-nodes then health transport-node-status <id> for any node not UP — flag nodes down ≥ 5 min; transient blips are normal
3. vmware-nsx inventory list-edge-clusters then health edge-cluster-status <id> — verify SR placement is balanced; one edge holding 80% of SRs is a single point of failure
4. vmware-nsx health alarms --severity HIGH (repeat with CRITICAL) — severity filter is exact-match, not "and above"
5. Cross-check with vmware-monitor for vSphere host events — a host losing connection to vCenter often masquerades as an NSX problem

Troubleshoot VM Connectivity

Judgment: connectivity failures happen at one of three layers. Identify which layer first, then drill — don't probe randomly.

• Layer 1 — VM-to-segment: VM has no segment, wrong vNIC, or port admin-down → troubleshoot vm-segment + troubleshoot port-status
• Layer 2 — segment-to-gateway: segment not attached to T1, T1 not connected to T0 → inventory get-tier1 shows no Tier-0 path
• Layer 3 — gateway-to-upstream: T0 BGP/static missing or SNAT not configured → networking bgp-neighbors, networking list-nat-rules

Steps (stop as soon as the failing layer is identified):

1. Layer 1: troubleshoot vm-segment my-vm-01 → if no port, check vSphere vNIC binding first
2. Layer 1: troubleshoot port-status <segment-id> → admin-down or DFW-blocked? If DFW, jump to vmware-nsx-security
3. Layer 2: inventory get-tier1 app-t1 → Tier-0 path present and route advertisement enabled? If not, T1↔T0 link broken
4. Layer 3: networking bgp-neighbors tier0-gw → all neighbors ESTABLISHED? Flapping → upstream issue
5. Layer 3: networking list-nat-rules app-t1 → SNAT rule covers the source CIDR? Mis-typed CIDR is the most common cause

Multi-Target Operations

All commands accept --target <name> to operate against a specific NSX Manager from your config (default: the first target in config.yaml), e.g. vmware-nsx inventory list-segments --target nsx-prod.

Usage Mode

MCP Tools (33 — 20 read, 13 write)

All MCP tools accept an optional target parameter to select which NSX Manager to connect to.

Write tools require explicit parameters and are audit-logged. The five delete_* tools preview by default: without confirm=True they return blast_radius (what would be removed, blockers, unmeasured) and change nothing. Show it to the user and pass confirm=True only after they decide; it is refused while a blocker remains or a read failed. Other MCP write tools execute directly — call one only after the user has explicitly asked for that change.

List results are envelopes — read truncated before you summarise

Every list-returning tool above returns {items, returned, limit, total, truncated, hint}, not a bare array. Rows live under items: empty items with truncated: false means the query genuinely matched nothing — report that, not a tool failure. truncated: true means items is not the whole collection — never call it complete. It does not mean more rows can be fetched: it stays true on the last page. Page with next_offset, stopping when it is null; hint says which situation you are in. Field semantics, total sourcing, and an example payload: references/capabilities.md.

Local & Small Models

Running with local or small models? See references/agent-guardrails.md for explicit operating rules that keep tool calls reliable.

CLI Quick Reference

# Inventory (read-only)
vmware-nsx inventory list-segments [--target <name>]
vmware-nsx inventory get-segment <segment-id>
vmware-nsx inventory list-tier0s
vmware-nsx inventory get-tier0 <tier0-id>
vmware-nsx inventory list-tier1s
vmware-nsx inventory get-tier1 <tier1-id>
vmware-nsx inventory list-transport-zones
vmware-nsx inventory list-transport-nodes
vmware-nsx inventory list-edge-clusters

# Networking (read-only)
vmware-nsx networking list-nat-rules <tier1-id>
vmware-nsx networking bgp-neighbors <tier0-id>
vmware-nsx networking list-static-routes <tier1-id>
vmware-nsx networking list-ip-pools
vmware-nsx networking ip-pool-usage <pool-id>

# Segment management (write; full option lists in references/cli-reference.md)
vmware-nsx segment create <id> --name <name> --tz <tz-path> [--vlan|--subnet] [--dry-run]
vmware-nsx segment update <id> [--name|--subnet] [--dry-run]
vmware-nsx segment delete <id> [--dry-run]

# Gateway management (write)
vmware-nsx gateway create-tier1 <id> --name <name> [--tier0|--edge-cluster] [--dry-run]
vmware-nsx gateway update-tier1 <id> [--name|--tier0|--advertise] [--dry-run]
vmware-nsx gateway delete-tier1 <id> [--dry-run]
vmware-nsx gateway configure-tier0-bgp <tier0-id> --local-as <asn> [--ecmp] [--dry-run]

# NAT (write)
vmware-nsx nat create-rule --tier1 <id> --rule-id <id> --action SNAT --source <cidr> --translated <ip> [--dry-run]
vmware-nsx nat delete-rule --tier1 <id> --rule-id <id> [--dry-run]

# Static routes (write)
vmware-nsx route create-static --tier1 <id> --route-id <id> --network <cidr> --next-hop <ip> [--dry-run]
vmware-nsx route delete-static --tier1 <id> --route-id <id> [--dry-run]

# IP pools (write)
vmware-nsx ip-pool create <pool-id> --name <name> --start <ip> --end <ip> --cidr <cidr> [--dry-run]

# Health & Troubleshooting (read-only)
vmware-nsx health alarms [--severity CRITICAL]
vmware-nsx health transport-node-status <node-id>
vmware-nsx health edge-cluster-status <cluster-id>
vmware-nsx health manager-status
vmware-nsx troubleshoot port-status <segment-id>
vmware-nsx troubleshoot vm-segment <vm-display-name>

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

Full CLI reference with all options and output formats: see references/cli-reference.md

Troubleshooting

"Segment not found" when querying

Segment display names and Policy API IDs can differ. Use vmware-nsx inventory list-segments to get the exact ID. The Policy API uses the segment id field, not display_name. Common mistakes: using the display name with spaces instead of the hyphenated ID.

NAT rule creation fails with "gateway not found"

NAT rules are created on Tier-1 gateways (or Tier-0 for some topologies). Verify the gateway name with vmware-nsx inventory list-tier1s. The gateway must have an edge cluster assigned for NAT to function.

BGP neighbor shows "Connect" or "Active" state

The BGP session is not established. Common causes:

1. Peer IP unreachable from the edge node — check physical uplinks and VLAN config
2. ASN mismatch — compare local and remote ASN in bgp-neighbors output
3. Firewall blocking TCP 179 — check edge node firewall rules (not NSX DFW)
4. MD5 password mismatch — verify authentication settings on both sides

Transport node status "degraded"

A transport node in degraded state has partial connectivity. Steps:

1. Check vmware-nsx health transport-nodes for the specific failure reason
2. Common cause: tunnel endpoint (TEP) unreachable — verify underlay MTU (minimum 1600 for Geneve)
3. Check NTP sync between NSX Manager and transport nodes
4. If recently upgraded, verify the host switch config matches NSX Manager expectations

"Password not found" error

The password environment variable is missing. Variable names follow the pattern VMWARE_NSX_<TARGET_NAME_UPPER>_PASSWORD where hyphens become underscores. Example: target nsx-prod needs VMWARE_NSX_NSX_PROD_PASSWORD. Check your ~/.vmware-nsx/.env file.

Safety

• Read-heavy: 20 of 33 tools are read-only (list, get, status, health, troubleshoot)
• Audit logging: All operations logged to ~/.vmware/audit.db (SQLite WAL, via vmware-policy) with timestamp, user, target, operation, parameters, and result
• Double confirmation: CLI write commands require two separate confirmation prompts before executing
• Dry-run mode: All CLI write commands support --dry-run to preview API calls without executing (MCP deletes preview unless confirm=True; other MCP writes execute directly and are audit-logged)
• Dependency checks: Segment delete refuses while ports are attached. Tier-1 delete first checks (read-only) for attached or Tier-1-scoped segments, NAT rules, static routes, service interfaces, extra locale-services, IPsec / L2 VPN services, a DNS forwarder and attached LB services; while any remain it refuses, deletes nothing and lists their ids (--dry-run runs the same check). Only a clean gateway has its default locale-service removed and is then deleted. IP pool delete (MCP) refuses while addresses are allocated
• Input validation: resource IDs restricted to letters, digits, - and _; NAT action checked against the allowed set; required fields checked (translated address for SNAT/DNAT/REFLEXIVE, CIDR + ranges per IP-pool subnet). CIDR/IP syntax and gateway existence are not checked client-side — they are left to NSX Manager's own API validation
• Prompt injection defense: NSX object names returned from the API are sanitized via _sanitize() — strips control characters, truncates to 500 chars
• Credential safety: Passwords loaded only from environment variables (.env file), never from config.yaml
• No firewall operations: Cannot create, modify, or delete DFW rules, security groups, or IDS/IPS policies — that scope belongs to vmware-nsx-security

Setup

uv tool install vmware-nsx-mgmt==1.15.1
vmware-nsx init      # writes ~/.vmware-nsx/config.yaml + .env (chmod 600), then verifies
vmware-nsx doctor

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

Full setup guide with multi-target config, MCP server setup, and Docker: see references/setup-guide.md

Architecture

User (natural language)
  |
AI Agent (Claude Code / Goose / Cursor)
  | reads SKILL.md
vmware-nsx CLI or MCP server (stdio transport)
  | NSX Policy API (REST/JSON over HTTPS)
NSX Manager
  |
Segments / Gateways / NAT / Routes / IP Pools / Transport Nodes

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/vmware-skills/VMware-NSX