VueScan-Mint-Firewall-Fix/README.md

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✅ Fixed: VueScan Can't Detect Brother Network Scanners on Linux Mint 22.1 — "ICMP admin prohibited filter" Solved
Body:
# Solved: VueScan Cannot Detect Brother Network Scanners on Linux Mint 22.1 / Ubuntu 24.04
## ✅ TL;DR
If VueScan doesnt detect your Brother network scanners unless your firewall is disabled, the issue is likely caused by firewalld zone policies silently rejecting traffic.
**Fix:** Move your network interface into the `trusted` zone.
---
## 🔧 Background
- **OS:** Linux Mint 22.1 “Xia” (Ubuntu 24.04 base)
- **Scanner:** Brother MFC and similar network models
- **Software:** VueScan
- **Firewall:** firewalld (nftables backend)
---
## 🐛 The Problem
Even with the correct ports open and Brother drivers installed, VueScan couldnt see the scanner.
Running `tcpdump` showed:
ICMP host <hostname> unreachable - admin prohibited filter
Despite:
- Opening all documented Brother ports (UDP 54925, TCP 54926)
- Adding direct rules, rich rules, and nftables manual rules
VueScan still couldnt discover any scanners.
---
## 🧠 Root Cause
Firewallds zone chain system (e.g., `filter_OUTPUT_POLICIES`, `filter_OUT_home`) overrides direct rules unless placed in the exact right spot. Traffic was still being rejected in a deep subchain.
---
## ✅ The Fix
Move your interface to the trusted zone to allow discovery without disabling the firewall.
```bash
sudo firewall-cmd --zone=trusted --change-interface=eno1 --permanent
sudo firewall-cmd --reload
Replace eno1 with your actual network interface (use ip a to check)
Then verify:
sudo firewall-cmd --get-active-zones
🎉 Result
VueScan now detects all Brother scanners on the network — no reboots required.
🔐 Security Note
This is safe if you're on a trusted home network behind a router. If you need more fine-grained access, you can create a custom firewalld zone to only allow specific IPs and ports.