IP address (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

inetnum: -
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 '' 

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.


There are two types of IP addresses, version 4 (IPv4) and version 6 (IPv6). IPv6 addresses still make up a relatively small percentage of internet addresses.

Example of a version 4 IP address:

Example of a version 6 IP address:


IP addresses in the wild

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

For a nameserver

In order for your your DNS (nameservers) 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
 nserver:	dns1.gandi.net
 nserver:	dns2.gandi.net
 nserver:	dns3.gandi.net

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

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 indicates something to the effect of “if you get a request for X domain, then point the user to X server.”

In BIND syntax, this is done using A records. It looks like this:

 @ 10800 IN A 

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

See also

Last modified: 08/03/2012 at 23:08 by Amy B. (Gandi)