firewall-config-diff

firewall-config-diff is a skill for Claude Code, Codex from fastrevmd-lab/fwskillsshare. It costs 53 tokens per session (2,463 once invoked), scanned A, original, MIT.

A tool for comparing two firewall configurations by the network rules and objects they represent, rather than by their exact text. Firewall configurations control which network traffic is allowed, blocked, or redirected.

In plain words
What is it for?
Checking configuration drift, comparing high-availability devices, validating migrations, and checking results before and after a firewall change.
Why use it?
It avoids treating harmless renames or reordering as changes and can reveal meaningful differences between configurations from different vendors.

Skill for Claude CodeCodex

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/fastrevmd-lab/fwskillsshare/firewall-config-diff
Any agent
npx skills add fastrevmd-lab/fwskillsshare --skill firewall-config-diff
Clone the repo
git clone --depth 1 https://github.com/fastrevmd-lab/fwskillsshare

Made for: Claude Code, Codex.

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 firewall-config-diff

README.md
[![agentmods](https://agentmods.dev/badge/skills/fastrevmd-lab/fwskillsshare/firewall-config-diff.svg)](https://agentmods.dev/skills/fastrevmd-lab/fwskillsshare/firewall-config-diff)
Your own site
<a href="https://agentmods.dev/skills/fastrevmd-lab/fwskillsshare/firewall-config-diff"><img src="https://agentmods.dev/badge/skills/fastrevmd-lab/fwskillsshare/firewall-config-diff.svg" alt="Measured on agentmods" height="20"></a>
Per session 53 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,463 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
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 $0.00053 $0.02463
Opus 5 $0.00026 $0.01231
Sonnet 5 $0.00011 $0.00493
Haiku 4.5 $0.00005 $0.00246

Measured 4d ago against content hash 7568f4d8a70b, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

firewall-config-diff scanned grade A with 0 findings 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 4d ago.

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.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

skills/firewall-config-diff/SKILL.md · 127 lines

How it starts

The opening of the file, as written. The whole thing — 127 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Firewall Config Diff

Overview

Use this skill to compare two firewall or NGFW configurations and report how they differ, by pivoting both through the parsing-* intermediate JSON schema. Each side is normalized to the same vendor-neutral sections — address_objects, address_groups, service_objects, service_groups, security_policies, nat_rules, zones, interfaces, static_routes / virtual_routers / routing, vpn_tunnels, ha_config, admin_users, and system — and then compared section by section. Because the comparison happens on the schema pivot rather than the raw text, same-vendor and cross-vendor diffs are one mechanism: the only cross-vendor addition is a normalization step for constructs that two vendors model differently.

The comparison is always semantic, never textual. Items are paired by what they mean — an address object by its value, a policy by its match-and-action tuple — so a rename, a reorder, or a different vendor's syntax does not register as a difference. A plain diff of two config files would flag every cosmetic and ordering change and miss the fact that two differently-named objects describe the same subnet; it would add nothing here and actively mislead. This skill compares meaning; it does not emit a target config (that is firewall-config-conversion) and does not judge the rulebase against best practice (that is firewall-best-practices-audit).

The output is always two parts: a per-section report listing what was added, removed, and changed, followed by a single parity verdict (EQUIVALENT or DIFFERENCES FOUND). Where a feature on one side has no equivalent on the other — common in cross-vendor comparisons — it is flagged not-comparable and excluded from the diff rather than reported as a false difference. The report never claims more than the schema supports and always lists what could not be compared.

Scope and routing

Compare two normalized parser outputs. Use a text-diff tool for literal line changes, firewall-config-conversion to emit target syntax, and firewall-best-practices-audit to assess one rulebase.

Read the full file on GitHub · 127 lines

Files

What ships with it

4 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. 4d ago First seen · 127 lines · 53 tokens per session scan A 7568f4d8a70b

Subscribe to this mod's changes

firewall-config-diff is a skill published in the GitHub repository fastrevmd-lab/fwskillsshare (8 stars, last pushed 7d ago), licensed MIT. It adds 53 tokens to every session and 2,463 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

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