====== Networking ======

===== useful programs =====
 
==== tcpdump ====

Tcpdump prints out a description of the contents of packets on a network interface that match the boolean expression..

Examples: 
  * dns:  $  tcpdump -i eth0 'udp port 53'
  * http:  $ tcpdump 'tcp port 80'
  * ftp:   $ tcpdump -i eth0 '(port 21 or 20)'


==== mtr - mytraceroute ====

mtmtr combines the functionality of the traceroute and ping programs in a single network diagnostic tool.r combines the functionality of the traceroute and ping programs in a single network diagnostic tool.


==== iptraf ====

iptraf  is  an  ncurses-based  IP LAN monitor GUI that generates various network statistics including TCP info, UDP counts, ICMP and OSPF information, Ethernet load info, node stats, IP checksum errors, and others...


==== iftop ====

iftop listens to network traffic on a named interface ... and displays a table of current bandwidth usage by pairs of hosts.

-i     interface

-p     Run in promiscuous mode

-P     Turn on port display

-F     net/mask  -- Specifies  a  network  for  traffic analysis


==== iperf ====

Measures the bandwith of a connections

  iperf -c iperf.ovh.net -m -i 1 -t 10 -r

It's usefull to check LAN Cables:
Connect two computers with the cable, setup static IP Addresses and start iperf on both:

Server mode on 1. box:
  iperf -s   

Client mode on 2. box:
  iperf -c <IP Address of box 1>


In the results you get the Banwidth:
  [  4] local <IP Addr node2> port 5001 connected with <IP Addr node1> port 2357
  [ ID] Interval       Transfer     **Bandwidth**
  [  4]  0.0-10.1 sec   6.5 MBytes   **305.2 Mbits/sec**