Troubleshooting network connectivity issues in Linux involves identifying and diagnosing the root cause of the problem by checking various network components and configurations. Here’s a systematic approach to troubleshoot network connectivity issues in Linux:

1. Check Physical Connections:
   • Ensure that all network cables are securely connected, and network interfaces (Ethernet, Wi-Fi) are properly seated in their respective ports.
2. Verify Network Interface Status:
   • Use the ip or ifconfig command to check the status of network interfaces.ip addr show orcssCopy codeifconfig -a
   • Ensure that the network interface is up (UP state) and has an IP address assigned.
3. Check IP Configuration:
   • Use the ip or ifconfig command to verify the IP address, subnet mask, gateway, and DNS server settings of the network interface.
   • Ensure that the IP configuration is correct and matches the network configuration of your environment.
4. Verify DNS Resolution:
   • Use the ping command to test DNS resolution by pinging a domain name.ping example.com
   • If DNS resolution fails, check the /etc/resolv.conf file for correct DNS server configurations and try using alternative DNS servers.
5. Test Local Network Connectivity:
   • Use the ping command to test connectivity to other devices on the local network by pinging their IP addresses.ping <IP_address>
   • If local pings fail, check the network configuration of the local device, including IP address, subnet mask, and gateway settings.
6. Check Firewall Settings:
   • Disable the firewall temporarily using the appropriate command for your firewall software (e.g., ufw disable for Uncomplicated Firewall).
   • If network connectivity improves after disabling the firewall, adjust firewall rules to allow necessary network traffic.
7. Inspect Routing Table:
   • Use the ip route command to view the routing table and ensure that the default gateway is configured correctly.ip route show
   • If necessary, add or modify routing entries using the ip route add command.
8. Check Network Services:
   • Verify that essential network services (such as DHCP client, network manager, and DNS resolver) are running using the systemctl command.systemctl status NetworkManager systemctl status systemd-resolved
   • Restart or troubleshoot network services as needed.
9. Review System Logs:
   • Check system logs (e.g., /var/log/syslog, /var/log/messages) for any network-related errors or warnings that may provide clues about the issue.bashCopy codetail -n 50 /var/log/syslog
10. Test Connectivity to External Resources:
    • Use the ping or traceroute command to test connectivity to external servers and websites.ping google.com traceroute google.com
    • If external pings or traceroutes fail, check for network issues outside your local network, such as ISP problems or internet service disruptions.

By following these steps and systematically checking network components and configurations, you can effectively troubleshoot and resolve network connectivity issues in Linux.