Dynamic DNS

Dynamic DNS or DDNS is the method to update, in real time, a DNS entry that points to a connection that has dynamic IP address. With this feature, if you have a connection with a service behind a dynamic IP address, you can use DDNS to reference the connection without being affected by changes in the IP address. So, even if the IP address changed, the DNS name remains unchanged.

The prices of this service are:

Activation rate
Annual rate
DDNS Service with a GRN connection 0€ 20€
DDNS Service without a GRN connection 0€ 10€
You need to add taxes to this prices
The activation rate doesn’t include the installation of the script in the client side

GRN’s DDNS client is a script for Linux systems. You can download this script to update DDNS entries here.
You can ask out about this service at admin@grn.cat.

Deploy to see a working example

Assume that the company “FSM” has a ADSL connection with a dynamic IP address. His manager wants to be able to connect to the computer at work from home using Terminal Server through a VPN connection. The problem begins when we can not configure the IP in the VPN connection because it is dynamic, we need a DDNS.


The company requests the DDNS service to GRN, which assigns the DNS fsm.dyn.grn.es to the company connection. The company has a GRN’s Linux-based firewall and they need to install the script that updates the DNS name. This script can be downloaded from here and have to be configured with the parameters GRN give you. You have to add an execution of this script in the cron system to check the IP and update the DNS name if it changes with the desired frequency.

From there, the manager of the company “FSM” can use a VPN that connects to the office through the use of the DNS entry fsm.dyn.grn.es