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Server Unreachable: Diagnostic Steps

Step-by-step guide to diagnosing server access issues using ping, SSH, port checks, firewall verification, and network routing analysis.

Read time: 12 min Troubleshooting
accesspingsshportfirewallconnectionserver
Author
REXE Teknoloji Network & Security Team
Editor
REXE Teknoloji Technical Editorial
First published
Last updated

Introduction

Being unable to access your server can stem from many different causes: network issues, firewall rules, service crashes, or hardware failures. In this guide, we'll walk through the steps you should follow to systematically diagnose server access issues.

Step 1: Ping Reachability Check

First, check if your server is reachable on the network:

hljs bash
# Simple ping test
ping -c 10 SERVER_IP

# Ping with timeout
ping -c 10 -W 3 SERVER_IP

Interpreting Ping Results

ResultMeaningPossible Cause
Replies receivedServer is reachable on networkIssue may be at service level
Request timeoutPackets not reaching destinationFirewall, network issue, or server down
Destination unreachableRouting issueWrong IP, network config error
100% packet lossComplete access lossServer down or no network connection

On REXE servers, when an IP has no rules at all, all ports are open. If your IP has rules, Default Block is automatically activated; in that case, ICMP (ping) may also require a rule (Ping toggle) from Path Panel.

Step 2: SSH Connection Test

If ping works, test the SSH connection:

hljs bash
# SSH connection test (verbose mode)
ssh -v root@SERVER_IP

# SSH with timeout
ssh -o ConnectTimeout=10 root@SERVER_IP

# SSH on specific port
ssh -p 2222 root@SERVER_IP

SSH Error Messages

hljs bash
# Connection refused — SSH service not running or wrong port
ssh: connect to host SERVER_IP port 22: Connection refused

# Connection timed out — Firewall blocking or server unreachable
ssh: connect to host SERVER_IP port 22: Connection timed out

# No route to host — Network routing issue
ssh: connect to host SERVER_IP port 22: No route to host

# Permission denied — Authentication failure
Permission denied (publickey,password)

Step 3: Port Access Check

Check if specific ports are open:

hljs bash
# Port check with telnet
telnet SERVER_IP 22
telnet SERVER_IP 80

# Port check with nc (netcat)
nc -zv SERVER_IP 22
nc -zv -w 5 SERVER_IP 80

# Port scan with nmap
nmap -p 22,80,443 SERVER_IP

Port States

StateMeaning
openPort is open and service is listening
closedPort is reachable but no service
filteredFirewall is blocking the port
timeoutConnection timed out

Step 4: Firewall Check

REXE Path Panel Check

On REXE servers, when an IP has no rules at all, all ports are open. When your IP has at least one rule, Default Block is automatically activated and the relevant port must be opened with a filter rule for access:

  1. Log in to Path Panel or the Rule Management product in your customer panel
  2. Click on the relevant IP address
  3. Verify filter rules exist for required ports
  4. Confirm rules are in propagated status

Path Panel rules may take 2-5 minutes to reach propagated status. Newly created rules may not be active immediately.

Even if the panel shows the rule as not yet propagated (not updated), the rule has most likely already been deployed within 2-5 minutes. The status may update with a delay due to the panel's status-check interval or the time it takes for the rule to be applied across all nodes on the Path side (except ours). This is only a visual delay in the panel; the port has in fact already been opened in the system.

Server-Side Firewall

If you have console access to the server:

hljs bash
# Check iptables rules
sudo iptables -L -n -v

# UFW status
sudo ufw status verbose

# firewalld status
sudo firewall-cmd --list-all

# nftables rules
sudo nft list ruleset

Temporarily Disable Firewall (For Testing)

hljs bash
# Disable UFW
sudo ufw disable

# Flush iptables rules
sudo iptables -F
sudo iptables -P INPUT ACCEPT
sudo iptables -P OUTPUT ACCEPT

Disabling the firewall leaves your server vulnerable. Use only for testing and re-enable immediately after.

Step 5: Service Status Check

If you have console access, check service status:

hljs bash
# SSH service status
sudo systemctl status sshd

# Web server status
sudo systemctl status nginx
sudo systemctl status apache2

# List all running services
sudo systemctl list-units --type=service --state=running

# List failed services
sudo systemctl list-units --type=service --state=failed

# Check listening ports
sudo ss -tlnp
sudo netstat -tlnp

Step 6: Network Routing Check

hljs bash
# Route analysis with traceroute
traceroute SERVER_IP

# Detailed analysis with mtr
mtr -r -c 50 SERVER_IP

# Local routing table
ip route show

Step 7: Console Access

If network access is unavailable, try alternative access methods:

REXE Customer Panel

  1. Log in to my.rexe.tr
  2. Click on the relevant service
  3. Use VNC Console or IPMI access
  4. Try the server restart option

Troubleshooting Checklist

hljs bash
#!/bin/bash
SERVER_IP="SERVER_IP_ADDRESS"

echo "=== Server Access Check: $SERVER_IP ==="

echo -e "\n[1] Ping Check:"
ping -c 5 -W 3 $SERVER_IP 2>&1 | tail -2

echo -e "\n[2] SSH Port (22) Check:"
nc -zv -w 5 $SERVER_IP 22 2>&1

echo -e "\n[3] HTTP Port (80) Check:"
nc -zv -w 5 $SERVER_IP 80 2>&1

echo -e "\n[4] HTTPS Port (443) Check:"
nc -zv -w 5 $SERVER_IP 443 2>&1

echo -e "\n[5] Traceroute:"
traceroute -m 15 $SERVER_IP 2>&1

echo -e "\n=== Check Complete ==="

Common Scenarios and Solutions

ScenarioPossible CauseSolution
Ping not working, no ports openServer down or no networkRestart server from REXE panel
Ping works but SSH won't connectSSH service crashed or port blockedCreate rule for SSH port in Path Panel
SSH connects but website won't loadWeb server service crashedConnect via SSH and restart nginx/apache
All ports show as filteredFirewall blocking all trafficCheck Path Panel rules
Intermittent connection dropsNetwork packet loss or DDoSTake mtr report, share with REXE support

Conclusion

Following a systematic approach is important for resolving server access issues. Start with ping checks and progressively verify port access, firewall rules, and service status. Don't forget to check Path Panel firewall rules on REXE servers. If the issue persists, contact REXE support with mtr reports and check results.

Frequently Asked Questions

I can't access my server at all, what should I do?

First check your server status from the REXE customer panel (my.rexe.tr). If the server is running, try accessing via VNC console. Check your firewall rules in Path Panel. If the issue persists, open a support ticket.

SSH connection gives 'Connection timed out' error?

This usually means the firewall is blocking the SSH port. Create a TCP Symmetric filter rule for SSH port (22) in Path Panel and wait for the rule to reach propagated status (2-5 minutes).

Server responds to ping but SSH doesn't work?

The SSH service may have crashed. Access the server via VNC console and restart the SSH service with 'sudo systemctl restart sshd'. Also check if the SSH port (22) has been changed.

I created a rule in Path Panel but still can't access?

Rules may take 2-5 minutes to reach propagated status. Check the rule status in Path Panel. Also make sure you selected the correct IP address, port, and protocol.

My server suddenly became unreachable, is it a DDoS attack?

Check attack logs in Path Panel. Null route may be active. REXE DDoS protection system activates automatically. If the attack continues, contact the support team.

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