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Linux commands - Network related

 Linux commands - Network related

This write up is a collection of some of the most commonly used linux commands used in the network related work. This is a short note and not a complete reference.

1. ifconfig / ip 

This command is used to find the network IP related information of the server.
'ip' is the latest update or the current command to be used on the latest version of the OS.

2. ping destination_host 

This is used to ping the destination server. Bacially, it will simply check the connection to the target.
You can interrupt the command with 'ctrl+c'.

3. telnet host port 

This command is used to connect to a specific port on the destination server.
This works better than the ping command as this will attemp to connect to the specified port. You can interrupt the command with 'ctrl+c'.

In some cases, when 'crtl+c' is not closing the telnet session, please use 'ctrl+]' and then enter 'close'.

4. nslookup google.com 

This is the short for Name server lookup.
This command can be used to check the DNS functionality of the network. This command will return you the details of the DNS server it is connecting to and the IP to which the queried domain name is resolved to.
To interpret the command result, the top 2 lines are normally for the DNS server and the below lines will tell you about the IP details of the queried host.

nslookup can also be used to do a reverse DNS lookup by querying the IP address.

5. host 

This is used to find the domain name given to any IP or the IP of a known domain name.
host 123.3.4.5
host mysubdomain.xyz.com

6. hostname 

This is used to find the hostname assigned to the current machine. You can use this command to set the hostname by passing the new name as an argument(sudo needed).

7. traceroute <destination> 

This is used to trace the network nodes through which the traffic flows on the way to the target. This will help identify where the latency is added the most in the network connection.

8. tcpdump 

This is used to collect the data and command packets sent through the  network interface. This collectes immence amount of data. So make sure you have enough storage to save the logs and you dont run this for a long time.

9. curl  

This is used to get the response from a web address.
you can use it to test the APIs. etc
The below option will save the response to a text file.
curl http://domain.com/test/ > /opt/mysoft/file2save.txt
To download files using curl
curl -o http://domain.com/test/file.txt
To set http methods and pass on http header parameters, use the options below. 
curl -X PUT -d header_param_1=value1 -d header_param_2=value2 http://domain.com/test/

10. wget 

This is used to download files from the destination.
wget http://domain.com/test/file.txt -O newTargetfile.txt


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