install ddclient:

ddclient is a Perl based client used
to update DNS entries. This client
works with all of our services as well
as services provided by many of our
competitors.

sudo apt-get install ddclient

when it starts to ask for parameters just click next and next ...

Now we have to configure 2 files, open a terminal and type the following :

sudo nano /etc/default/ddclient

# Configuration for ddclient scripts

# Generated from debconf on Mon Aug 2 12:39:39 CEST 2010

#

# /Etc/default/ddclient



# Set to "true" if ddclient run Should Be Every time a new ppp connection is

# Established. This Might Be Useful, if You are using dial-on-demand.

run_ipup = "false"



# Set to "true" if ddclient Should run in daemon mode

# If tis is changed to true, run_ipup Must Be Set to false.

run_daemon = "true"



# Set the time interval Between the updates of the dynamic DNS name in seconds.

# This option only Takes effect if the ddclient runs in daemon mode.

daemon_interval = "300"

now with the other:

sudo nano /etc/ddclient.conf

# #

# # OpenDNS.com account-configuration

# #



ssl = yes

use = web, web = whatismyip.org



server = updates.opendns.com

protocol = dyndns2

login = username in OpenDNS                   <-----

password = 'key OpenDNS'                      <----- CHANGE THIS

(Name of the network you set up in OpenDNS)   <-----

And configure your DNS as describe JE2Tom in his post.