Linux Networking: A Simplified Guide to IP Addresses and Routing

Getting started with Linux network configuration: IP address and routing

For every Linux enthusiast or administrator, configuring or troubleshooting network settings is common. Although this process may seem scary, you can easily master the Linux network configuration and benefit greatly from it by mastering the right knowledge and tools. This guide will explore the basics of configuring IP addresses and routing on Linux systems.

Basic network concept

• What is the IP address?

Each device connected to the network has a unique identifier called an IP address. It is like the "address" in the huge interconnected world of the Internet.

 <code>* **IPv4与IPv6：**虽然IPv4仍然很普遍，但它的继任者IPv6提供了更大的地址空间和改进的功能。IPv4地址看起来像192.168.1.1，而IPv6地址类似于1200:0000:AB00:1234:0000:2552:7777:1313。 * **公网IP与私网IP：**公网IP在全球范围内是唯一的，可以直接通过互联网访问。私网IP保留用于内部网络使用，不能在公共互联网上路由。</code>

• Subnet mask and gateway

The subnet mask determines which part of the IP address is the network and which part of the host. The gateway (usually a router) connects the local network to an external network.

• routing

The core mechanism of routing is to determine how data arrives from sources to destinations between Internet networks.

Network configuration tools in Linux

Linux provides traditional tools such as ifconfig and route, as well as modern tools such as IP, nmcli and nmtui. The choice of a tool usually depends on the specific distribution and administrator preferences.

NetworkManager and systemd-networkd also modernize network management, providing CLI and GUI tools for configuration.

Configuring IP Address in Linux

1. Use the ip command:

   • Show current configuration: ip addr show
   • Assign static IP: ip addr add 192.168.1.10/24 dev eth0
   • Delete IP address: ip addr del 192.168.1.10/24 dev eth0

2. Using nmcli (NetworkManager):

   • Show connection details: nmcli connection show
   • Setting up static IP: nmcli con mod "连接名称" ipv4.addresses "192.168.1.10/24" ipv4.method manual
   • Activate the connection: nmcli con up "连接名称"

3. Use GUI Tools: Different Linux distributions come with different desktop environments. Most of these environments provide intuitive network configuration utilities.

Configuring routing in Linux

1. Understand the routing table: The routing table contains rules to determine the destination of network traffic. To view it, use: ip route show

2. Modify the routing table:

   • Add route: ip route add 192.168.2.0/24 via 192.168.1.1
   • Delete the route: ip route del 192.168.2.0/24
   • Change the default gateway: ip route add default via 192.168.1.1

3. Use nmcli for routing:

   • Show route: nmcli connection show "连接名称" | grep route

Automatic IP configuration: DHCP

DHCP automatically assigns IP addresses and other network configurations to the device. This dynamic approach eliminates the need for manual configuration.

To request a DHCP lease: dhclient eth0

Notes on IPv6

While IPv4 still dominates, IPv6 is on the rise. A distinctive feature of IPv6 is its link-local addresses, which are automatically configured for each interface and are used for local communication.

troubleshooting

Commonly used troubleshooting tools include:

• ping : Check the accessibility of the host.
• traceroute : Tracks the path of the packet to the network host.
• netstat : Display network connections, routing tables, etc.

Network configuration security

To protect your Linux system, use a firewall like ufw or iptables. Also, make sure your software is updated regularly to patch vulnerabilities and to adopt good security measures.

in conclusion

Through the understanding and practical operation of basic knowledge, Linux network configuration will no longer be so daunting. Although challenges may occur, you can easily deal with the interconnection of Linux networks with the knowledge and tools.

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