Shell network operations

$dhclientethN

Example: Static configuration of IP address

Of course, you can also consider using static configuration.

 ip_address

It's localhost

 IP

address,

 gw_ip_address

It is the gateway to the network.

 IP

address.

 $ ifconfig eth0 ip_address on$ route add deafult gw gw_ip_address

If the above doesn't work, remember to pass

 ifconfig/mii-tool/ethtool

Wait for the tool to check whether the network card is driven, and then pass

 lspci/dmesg

Wait to check the network card type (or check the motherboard manual and the manual that comes with the independent network card), then install or compile the relevant driver, and finally pass the driver

 insmod/modprobe

Wait for the tools to be loaded into the kernel.

Build a network bridge using Linux

The bridge works in

 OSI

The second layer of the model, the data link layer, only needs to know the target host’s

 MAC

The address will work. The Linux kernel is in

 2.2

This function has been supported since the beginning. Please refer to the subsequent reference materials for specific configuration instructions. If you want to configure the Linux host as a network bridge, you need at least two network cards.

The function of a network bridge is equivalent to a network cable. Users do not need to care about what is inside. By connecting its two network ports to two hosts, the two hosts can communicate with each other. However, it is more powerful than a network cable. If it is equipped with a firewall, it can isolate the network segments connected to both ends of it (note that this is a network, because it does not recognize

 IP

), in addition, if the bridge has multiple network ports, a switch with complex functions can be implemented, and if multiple bridges are effectively combined, it is possible to implement a complex firewall system that can achieve flow control and load balancing.

Using Linux for routing

Routing works in

 OSI

The third layer of the model, the network layer, passes

 router

Linux routing can be configured. Of course, there are many tools under Linux that support dynamic routing. Relevant information is overwhelming on the Internet. Due to time constraints, I will not introduce it here.

Use Linux to build various conventional network services

What network services are needed?

Get one for the LAN

 DHCP

Server, then get one

 dhcpd

, look at the references;

If you want to get an email sending server, then install it

 sendmail

or

 exim4

;

If you want to get a mailing list server again, then install one

 mailman

;

If you want to get a server that receives mail, then install one

 pop3

server;

If you want to get one

 web

site, then get one

 apache

or

 nginx

server;

If you want to get the firewall service, then use

 iptables

Tool configuration

 netfilter

That's it

What's more? If you can think of it, there is basically a corresponding implementation on Linux.

Diagnosis and maintenance of network problems under Linux

If a network problem occurs, don’t panic. Check each layer of the network step by step: physical link, link layer, network layer, and application layer. Be familiar with using various tools, including

 ethereal/tcpdump

,

 hping

,

 nmap

,

 netstat

,

 netpipe

,

 netperf

,

 vnstat

,

 ntop

wait.

For detailed usage of these tools and related knowledge on network problem diagnosis and maintenance, please see the subsequent related information.

Network programming and development under Linux

If you want to do network programming development, for example:

To implement a client

 /

For server architecture applications, you can use Linux

 socket

programmed;

If you want to write a program for packet capture and protocol analysis, you can use

 libpap

etc. function library;

If you want to implement a certain protocol, you can refer to the relevant

 RFC

documentation and pass

 socket

Programming to achieve.

You can refer to the relevant

 Linux socket

Programming and other information.

postscript

It originally introduced some basic content related to the network, but due to time constraints, it was not elaborated. For more details, please refer to relevant materials.

At this point, the entire "Shell Programming Paradigm" has been roughly completed, but the "Example" lacks examples, especially in this section. Therefore, if time permits, some examples will be added gradually.

References

Computer Networks—A Top-Down Analysis Approach

Linux Network Architecture (Published by Tsinghua University Press)

Linux System Troubleshooting and Troubleshooting Chapter 13 Network Problems (People's Posts and Telecommunications Press)

Dial-up Internet access using ADSL under Linux

Collection of relevant information on wireless networks under Linux

Implementation analysis and use of Linux bridge

DHCP mini howto

The best 75 security tools

What network administrators must know

Two tools for detecting rootkits on Linux: Rootkit Hunter and Chkrootkit

Simple analysis of packet capture and ip protocol (based on pcap library)

RFC

C language programming implementation example of HTTP protocol