How to troubleshoot networks in CentOS

CentOS System Network Troubleshooting Guide

This article will guide you on how to systematically troubleshoot and resolve network failures in CentOS systems.

1. Preliminary inspection

1. Physical connection: First, check whether the network cable connection is firm and whether the network equipment (router, switch, etc.) is operating normally.

2. Command line diagnosis

The following steps will be used to diagnose using the command line tool:

1. Network connection testing: Use the ping command to test connectivity with the remote host. For example, ping www.example.com . Failure to ping may indicate a network failure.

2. IP address and gateway settings: Use ip addr or ifconfig command to check the network interface configuration to confirm whether the IP address, subnet mask and gateway are correct.

3. DNS resolution: Use nslookup or dig command to check whether the domain name resolution is normal. For example, nslookup www.example.com .

4. Firewall Settings: Use iptables (or firewall-cmd , depending on your firewall configuration) to check if the firewall rules block network connections. If necessary, temporarily disable the firewall to eliminate its interference (operate with caution, please restore it in time after disabling).

5. Network service status: Use systemctl status network (or related network services, such as systemctl status NetworkManager ) to check whether the network service is operating normally. If it is not running, start it with systemctl start network (or related services).

6. Advanced diagnostic tools:

   • traceroute (or traceroute6 ): Tracks the path of the packet to the target host and helps identify network bottlenecks or failure points.
   • netstat : Displays network connection, routing table, interface statistics and other information to provide more detailed network status.

3. Network equipment inspection

If the above steps fail to resolve the problem, you may need to check the network device (router, switch, etc.) or network lines. Consider replacing the network cable or contacting the network equipment supplier for help.

4. Summary of troubleshooting process

1. Physical connection check
2. Network interface configuration check ( ip addr or ifconfig )
3. DNS resolution check ( nslookup or dig )
4. Firewall settings check ( iptables or firewall-cmd )
5. Network service status check ( systemctl status )
6. Network equipment inspection

Through the above steps, you can effectively troubleshoot network failures in CentOS system. If the problem persists, you may need to check the hardware further or contact your network service provider.

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