Troubleshooting Network Connectivity Issues

A systematic approach to diagnosing why your server or service is unreachable.

Step 1 — Can You Ping the Server?

ping -c 4 YOUR_SERVER_IP

• If ping succeeds: the server is online. The issue is service-level.
• If ping fails: the server may be down, the IP is wrong, or ICMP is blocked by firewall.

Step 2 — Trace the Network Path

traceroute YOUR_SERVER_IP    # Linux/macOS
# or:
mtr YOUR_SERVER_IP           # Better live traceroute (apt install mtr)

Look for where packets stop responding — that indicates the problem hop.

Step 3 — Is the Service Listening?

ss -tulpn | grep 80    # Is Nginx listening on port 80?

Step 4 — Is the Firewall Blocking It?

ufw status                    # Check UFW rules
iptables -L -n -v | head -30  # Raw iptables rules

Step 5 — Test Port Connectivity from Outside

nc -zv YOUR_SERVER_IP 80    # Test TCP port 80

Step 6 — Check DNS Resolution

dig yourdomain.com
nslookup yourdomain.com

Compare the resolved IP with your server's actual IP.

Step 7 — Check Service Logs

journalctl -u nginx -n 50
tail -f /var/log/nginx/error.log

Step 8 — Review Network Interface Stats

ip -s link show eth0

Look at RX/TX error and drop counts — high numbers indicate a hardware or driver problem.