linux network commands

The network commands chapter explains various tools which can be useful when networking with other computers both within the network and accross the internet, obtaining more information about other computers. This chapter also includes information on tools for network configuration, file transfer and working with remote machines.

netstat

Displays contents of /proc/net files. It works with the Linux Network Subsystem, it will tell you what the status of ports are ie. open, closed, waiting, masquerade connections. It will also display various other things. It has many different options.
tcpdump

This is a sniffer, a program that captures packets off a network interface and interprets them for you. It understands all basic internet protocols, and can be used to save entire packets for later inspection.
ping

The ping command (named after the sound of an active sonar system) sends echo requests to the host you specify on the command line, and lists the responses received their round trip time.

You simply use ping as:

ping ip_or_host_name

Note to stop ping (otherwise it goes forever) use CTRL-C (break).
Note Please note


Using ping/smbmount/ssh or other UNIX system programs with a computer name rather than IP address will only work if you have the computer listed in your /etc/hosts file. Here is an example:

192.168.1.100 new

This line says that their is a computer called “new” with IP address 192.168.1.100. Now that it exists in the /etc/hosts file I don't have to type the IP address anymore, just the name “new”.
hostname

Tells the user the host name of the computer they are logged into. Note: may be called host.
traceroute

traceroute will show the route of a packet. It attempts to list the series of hosts through which your packets travel on their way to a given destination. Also have a look at xtraceroute (one of several graphical equivalents of this program).

Command syntax:

traceroute machine_name_or_ip

tracepath

tracepath performs a very simlar function to traceroute the main difference is that tracepath doesn't take complicated options.

Command syntax:

tracepath machine_name_or_ip

findsmb

findsmb is used to list info about machines that respond to SMB name queries (for example windows based machines sharing their hard disk's).

Command syntax:

findsmb

This would find all machines possible, you may need to specify a particular subnet to query those machines only...
nmap

“ network exploration tool and security scanner”. nmap is a very advanced network tool used to query machines (local or remote) as to whether they are up and what ports are open on these machines.

A simple usage example:

nmap machine_name

This would query your own machine as to what ports it keeps open. nmap is a very powerful tool, documentation is available on the nmap site as well as the information in the manual page.