======Networking Commands=====

===Transfer files with low bandwidth===

Transfer large files/directories with no overhead, over the network 

  # ssh user@host "cd targetdir; tar cfp - *" | dd of=file.tar


===Identify Network Cards===

Causes traffic lights to flash on the nic

  # ethtool -p ethX
  

===Watch Data output===

Watch Data Usage on eth0

  # watch ifconfig eth0



===Show Open Ports===

netcat as a portscanner. Show open ports.

  # nc -v -n -z -w 1 127.0.0.1 22-1000



===Show Listening ports===

Lists all listening ports together with the PID of the associated process

  # netstat -tlnp



===Show activity on a port===

what's running on a given port on your machine

  # lsof -i -n -P | grep :22



===SSH Tunnel===

Start a tunnel from some machine's port 80 to your local post 2001

now you can access the website by going to http://localhost:2001/

  # ssh -N -L2001:localhost:80 somemachine



===SSH Tunnel via ...===

If you want to connect to server behind the DMZ, you can use a intermediate. This is useful where your have your local machine outside a firewall; a visible machine on the DMZ; and a third machine invisible to the outside. 

  # ssh -f -N -q -L 80:192.168.1.69:80 username@dmz.example.com



The params explaination:

  * -f tells ssh to go into the background (daemonize).

  * -N tells ssh that you don't want to run a remote command (that is, you only want to forward ports)

  * -q tells ssh to be quiet

  * -L specifies the port forwarding