====== Definition ======

An IP (Internet Protocol) address is a numerical name that is assigned to a machine so that other machines can find it and communicate with it over the internet. 


IP addresses are unique, meaning that there is only one per machine (or virtual machine, as in the case of a Gandi virtual server). 


Just like domain names, each IP address is registered to a person or organization. You can perform a whois lookup of an IP Address to see information about it. For example, here is a whois look-up of 217.70.177.39:


  inetnum:        217.70.176.0 - 217.70.183.255
  netname:        GANDI-NET1
  descr:          GANDI SERVERS
  country:        FR
  admin-c:        NG183-RIPE
  tech-c:         NG183-RIPE
  notify:         noc@gandi.net
  mnt-by:         GANDI-NOC
  changed:        mik+ripe@gandi.net 20070817
  source:         RIPE
  status:         ASSIGNED PA
  
  role:           NOC Gandi
  address:        GANDI
  address:        15 place de la Nation
  address:        75011 Paris
  e-mail:         noc@gandi.net
  admin-c:        FLD-RIPE
  tech-c:         FLD-RIPE
  nic-hdl:        NG183-RIPE
  mnt-by:         GANDI-NOC
  remarks:        -------------------------------------------------
  remarks:        GANDI is an ICANN accredited registrar
  remarks:        for more information:
  remarks:        Web:   http://www.gandi.net
  remarks:        -------------------------------------------------
  remarks:        - network troubles: noc@gandi.net
  remarks:        - SPAM complaints: abuse@gandi.net
  remarks:        -------------------------------------------------
  source:         RIPE
  changed:        fld@gandi.net 20070906 
  
  % Information related to '217.70.176.0/20AS29169' 
  
  route:        217.70.176.0/20
  descr:        GANDI is an ICANN accredited registrar
  descr:        for more information:
  descr:        Web:   http://www.gandi.net
  origin:       AS29169
  notify:       noc@gandi.net
  mnt-by:       GANDI-NOC
  changed:      lfrigault@gandi.net 20030731
  source:       RIPE

 
This information allows you to see who is responsible for the machine, and where you can send abuse complaints or find other useful information about the IP address.



====== Examples ======
There are two types of IP addresses, version 4 (IPv4) and version 6 (IPv6). IPv6 addresses only make up a very small percentage of internet addresses.


Example of a version 4 IP address:

  217.70.184.1



===== IP addresses in the wild =====
Here are just two of many examples of IP addresses in action.


==== For a name server ====

In order for your your DNS (name servers) to work, they need to be registered at the registry so that the host name is associated with an actual machine. This is done by creating a glue record for your name server. 

When looking up a domain name in the whois database, these glue records appear as such:

   nserver:	dns0.gandi.net 217.70.177.39
   nserver:	dns1.gandi.net 217.70.177.45
   nserver:	dns2.gandi.net 217.70.177.46
   nserver:	dns3.gandi.net 217.70.179.36

So, for example, the IP address of the name server dns0.gandi.net is 217.70.177.39. This means that the actual machine where the DNS server is physically located is called 217.70.177.39.


==== For a web server ====
So that your website can be visible on the web, your DNS need to know where to point the domain name. This is done by creating a record in your DNS zone file that says something to the effect of "if you get a request for X domain, then point the user to X server". 

In BIND syntax this looks like:

   @ 10800 IN A 217.70.184.34 

Thus, in the above example, the IP address of the server where the website is physically hosted is called 217.70.184.34.