Linux Network Management

2-3:
Ifconfig can only view the ip/broadcast address/mask/MAC address of the network card, but cannot see the gateway address and DNS address;
Disable/enable NIC
Ifdown [NIC device name]//disable network card;
ifup [NIC device name]//enable network card;

netstat [options]

①-T: List TCP protocol ports;

②-u: List UDP protocol ports;

③-n: Use IP address and port number, without using domain name and service name;

④-l: List only in the listening state of the network service;

⑤-A: List all network connections;



3-1:

Ifconfig

View and configure the network Status command; (only the IP and subnet masks can be viewed)


To turn off and start the network card:
①ifdown network card Device name//disable network card device;
②ipup network card device name//enable network card device;


Querying network Status:
①netstat Options
Options:
-T: Lists TCP protocol ports;
-U: Lists UDP protocol ports;
-N: Do not use domain name and server name, but use IP address and port number;
-L: List only the network service in the listening State;
-A: Lists all network connections;
State:
LISTEN (Listening status)
Established (indicates that the connection already exists)

②netstat-an | grep established | Wc-l//view current system remote connection number;

Netstat-rn and Route-n
Option-r: Lists the routing list with the same functionality as the route command (the last ③gateway is the gateway address of the NIC);

！！ In a server, even the network card is unable to set the gateway!!!
！！ When you have finished using the Remote connection tool, use logout to exit when you close the software!!!

Domain Name resolution command:


①nslookup [domain name and IP]//For Domain name and IP address resolution;


②[[email protected]~] #nslookup
> Server
View the DNS server for this computer;
> Exit
Exit the nslookup command;
3-2 notes:

ping command:
Ping ip or domain name [options]//probe the network status of the specified IP or domain name;
Options:
-C Number of times: Specifies the number of ping packets;

Telnet command:
Telnet is a non-encrypted plaintext connection, Linux has been almost encrypted by SSH remote connection replacement, although not for remote, but still can be used for port detection;

telnet [domain name or IP] [port]//remote management and Port detection command;


traceroute command:
traceroute [options] IP or domain name//route tracking command;
Options:
-N: Use IP, do not use domain name, faster;
！！ The network test commands are almost always using the ICMP (Internet Control message Protocol) Internet Controlling message Protocol!!!


wget command:
wget file//download command;


tcpdump command:
Tcpdump-i ETH0-NNX Port 21
Options:
-I: Specify the NIC interface;
-NN: The domain name and service in the packet are converted to IP and port;
-X: Displays the contents of the packet in 16 binary and ASCII code;
-port: Specifies the listening port;

4-1:

Encryption algorithm:
① Symmetric encryption algorithm:
Using the encryption method of single-key cryptosystem, the same key can be used as information encryption and decryption, which is called symmetric encryption, also known as key encryption;

② Asymmetric Encryption algorithm:
Asymmetric encryption Algorithm (symmetric cryptographicalgorithm) aka "Public Key Encryption algorithm", asymmetric encryption algorithm requires two keys: Public key (Plublickey) and private key (Privatekey)

SSH command:
①SSH User name @ip//remote management of the specified Linux server;
② when using SSH to remotely connect to a computer, the downloaded offset key is stored in the home directory of the local current user, in a hidden file named. ssh;
③SCP [-r] User name @ip: File path Local path//download file;
④SCP [-r] Local file username @ip: Upload path//upload file;
⑤-r: If the uploaded or downloaded object is a directory, you need to add-r, the file does not need to add-r;


4-2:

SECURECRT Remote management tools:
Normal font: New song body
Character Set: GB2312 Chinese
Caracter Encding:utf-8 (International Code)

4-3:
Xshell (remote Administration tools) and WINSCP (File Transfer tool)

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Linux Network Management