A tale of dashboards, SSH connections, and the irony of security systems
When your monitoring system becomes the monitored - a debugging story that perfectly illustrates how security measures can protect against themselves, creating a beautiful paradox in network administration.
Our story begins with a simple problem: a fail2ban monitoring dashboard showing the dreaded "Error fetching logs" message. What seemed like a straightforward PHP/SSH configuration issue would soon reveal itself to be something far more interesting...
Problem Identified: Dashboard on the-lab cannot fetch logs from web-node
Time for some network detective work. Let's see what's happening with that SSH connection...
Network Analysis: Testing connectivity and port status
Port 22 is closed! But wait... SSH was working just minutes ago!
Contradiction Discovered: Direct access to web-node shows SSH is actually running
The plot thickens - SSH is running on web-node, but the-lab can't connect to it.
SSH is running on web-node, but the-lab can't connect. Looking at the SSH logs reveals the shocking truth...
The fail2ban dashboard was banned by fail2ban itself!
Our fail2ban system did exactly what it was designed to do - protect against brute force attacks. The PHP dashboard, trying to connect without proper key authentication, triggered multiple failed attempts and got banned!
Fail2ban Status Check:
There it is - 192.168.1.XXX (the-lab) is officially banned by its own monitoring target!
With the mystery solved, the fix was simple - unban the dashboard server!
Unbanning the-lab:
Success! The dashboard server is now free to connect again.
The dashboard immediately started working again. The final test showed the complete story in the fail2ban logs:
Here's the complete story as told by the fail2ban logs:
the-lab, web-node, lab-node
Before banning occurred
Both lab-node and the-lab
From problem to resolution
Fail2ban works perfectly: The system correctly identified and banned brute force attempts, demonstrating effective intrusion prevention.
Monitoring can be monitored: Even security dashboards aren't immune to the systems they monitor - a perfect example of recursive security.
Check the logs: The SSH service logs revealed the true story behind the connection failures, highlighting the importance of systematic log analysis.
Network debugging process: Systematic testing (nmap, systemctl status, log analysis) led to the solution rather than assumptions.
Beautiful irony: Sometimes the thing you're monitoring is what's blocking you from monitoring it - a perfect cybersecurity paradox!