Troubleshooting Network Connectivity Print

Network issues can be frustrating. This guide provides a systematic approach to diagnose and resolve common network connectivity problems on your server, ranging from basic checks to more advanced diagnostics.

1. Introduction
   • When your server can't connect to the internet, or clients can't reach your server, it indicates a network connectivity issue. This article will help you identify the root cause using standard troubleshooting tools and practices.
2. Initial Checks & Basic Tools
   • Is the Server On and Running?
     • For VPS: Check your WHMCS client area or provider's control panel (ServerHood.com) to ensure your VPS is in a "Running" state and not suspended.
     • For Dedicated Servers: Verify power status, and check the front panel or remote management (IPMI/KVM) for activity.
   • Check Physical Connection (Dedicated Servers Only):
     • Are the network cables securely plugged into the server's NIC (Network Interface Card)?
     • Are the link lights on the NIC active?
     • Contact ServerHood.com if you suspect a physical issue in the data center.
   • Verify IP Configuration:
     • Linux:ip a # Check IP address, subnet, gateway. Ensure interface is 'UP'.
     • Windows Server:ipconfig /all # Check IP, subnet, gateway, DNS servers.
     • Confirm the IP configuration matches what ServerHood.com has assigned to your server.
   • Loopback Test (Verify TCP/IP Stack):
     • ping 127.0.0.1 (IPv4) or ping ::1 (IPv6)
     • Expected result: Successful replies. If this fails, your server's TCP/IP stack is severely corrupted, requiring more drastic troubleshooting (OS reinstallation might be quicker).
   • Ping Default Gateway (Verify Local Network):
     • ping [your_gateway_ip] (e.g., ping 192.168.1.1)
     • Expected result: Successful replies. If this fails, your server can't reach the local network router. Check cabling (dedicated), virtual network settings (VPS), or gateway configuration.
   • Ping External IP Address (Verify Internet Connectivity):
     • ping 8.8.8.8 (Google's DNS) or ping 1.1.1.1 (Cloudflare's DNS)
     • Expected result: Successful replies. If this fails but gateway ping works, there's an issue beyond your local network (e.g., provider outage, network-level firewall, or your server's firewall blocking outbound pings).
   • DNS Resolution Test:
     • If ping 8.8.8.8 works, but ping google.com fails, your server likely has a DNS resolution issue.
     • Linux:dig google.com # or 'host google.com'cat /etc/resolv.conf # Check configured DNS servers
     • Windows Server:nslookup google.com
     • Solution: Ensure correct DNS server IPs are configured in your network settings.
3. Common Issues & Solutions
   • "Destination Host Unreachable" or "Request Timed Out" (Ping Failures):
     • Incorrect IP/Subnet/Gateway Configuration: Revisit "Configuring Network Interfaces" and double-check all parameters. A single typo can break connectivity.
     • Server's Firewall Blocking Traffic:
       • Your server's firewall (Iptables, UFW, FirewallD on Linux; Windows Firewall) might be blocking ICMP (ping) or other traffic.
       • Temporarily Disable (CAUTION!): For testing, you might temporarily disable the firewall (e.g., sudo ufw disable, sudo systemctl stop firewalld, or disable Windows Firewall profile) to see if connectivity resumes. Re-enable immediately after testing!
       • Add Rules: Add explicit rules to allow the necessary traffic (e.g., ports 80, 443, 22).
     • Provider Firewall: Some providers have a network-level firewall. Check their control panel.
     • Network Interface Down:
       • Linux: Use ip link show to ensure your adapter is UP. If not, try sudo ip link set [interface_name] up or sudo ifup [interface_name] (legacy) / sudo nmcli connection up [connection_name].
       • Windows: Check adapter status in Network Connections. Right-click and "Enable" if disabled.
     • Provider Network Issue: If all server-side checks pass, the issue might be with ServerHood.com's network infrastructure. Contact support.
   • Website/Service Not Accessible (but Server Pings Fine):
     • Service Not Running: The web server (Apache, Nginx, IIS) or database server (MySQL, PostgreSQL, MSSQL) might be down.
       • Linux: sudo systemctl status [service_name] (e.g., apache2, nginx, mysql). Start if needed: sudo systemctl start [service_name].
       • Windows: Check "Services" app (services.msc) or Task Manager for the service status.
     • Service Listening on Wrong IP/Port:
       • Use netstat to verify which IP addresses and ports your services are listening on.
       • Linux: sudo netstat -tuln (TCP, UDP, Listening, Numeric). Look for 0.0.0.0:[port] or [your_server_ip]:[port].
       • Windows: netstat -ano (shows listening ports and process IDs).
     • Firewall Blocking Specific Port: Ensure your server's firewall explicitly allows inbound connections on the service's port (e.g., 80 for HTTP, 443 for HTTPS, 22 for SSH, 3389 for RDP).
     • DNS Issues (Client-side/External):
       • Has the domain's DNS A/AAAA record propagated to the public DNS servers? Use online DNS propagation checkers.
       • Clear your local machine's DNS cache if you recently updated DNS.
   • Slow Connectivity / Packet Loss:
     • Traceroute/Tracert:
       • traceroute google.com (Linux) / tracert google.com (Windows)
       • This command shows the path packets take and identifies where latency or packet loss might be occurring (e.g., specific router hops).
     • Bandwidth Exhaustion: Check server resource monitoring tools (e.g., htop, nload on Linux; Task Manager on Windows) for high network usage.
     • DDoS Attack: If you suspect a denial-of-service attack, contact ServerHood.com support immediately.
4. When to Contact ServerHood.com Support:
   • If you've performed all the above checks and still can't resolve the issue.
   • If you suspect an outage or hardware failure outside your server's direct control.
   • If you're locked out of your server due to misconfiguration and require out-of-band access.
   • When contacting support, provide them with detailed information: the problem description, steps you've already taken, and the output of any diagnostic commands.
5. Conclusion
   • Effective network troubleshooting requires patience and a systematic approach. By utilizing the tools and methods outlined, you can diagnose and resolve most common network connectivity issues on your ServerHood.com VPS or Dedicated Server.