# Dynamic DNS

Dynamic DNS (DDNS) is a mechanism that allows clients to dynamically update IP addresses for registered domain names. This is useful when an ISP uses PPP, DHCP, or XAuth to dynamically change the IP address for a CPE router (such as a security device) that protects a webserver. Internet clients can reach the webserver by using a domain name even if the IP address of the security device has previously changed dynamically. This is made possible by a DDNS server (such as dyndns.org or ddo.jp), which maintains a list of the dynamically changed addresses and their associated domain names. The device updates these DDNS servers with this information periodically or in response to IP address changes.

To use DDNS, create an account (username and password) on the DDNS server. The server uses this account information to configure the client device.

This page describes how to initiate or delete the DDNS module entries in the DDNS Entries table. Each entry represents a module that allocates all resources needed for DDNS. Deleting an entry frees the resources.

Note: To see the DDNS table, you need to set either of the following options:

Config DDNS Client: Specifies that the DNS has Dynamic DNS capability.

Enable DDNS Client: Enables DDNS functionality.

DDNS Entries Table

ID The identification number of the entry in the DDNS Entries table. The range for this value is 1–256.

Server Type The kind of DDNS server to use. You can choose between the ddo and dyndns server types.

Server Name The fully qualified domain name (FQDN) of the DDNS server. The maximum length is 63 characters.

Username The username of the DDNS account. The maximum length is 63 characters.

Interface The interface through which the device communicates with the DDNS server.

Next-Update The minimum period (expressed in minutes) between updates. The default is 10 minutes, and the allowable range is 1–1440.

Last-Response The status of the last response transmitted by the DDNS server (such as "NoChange," "Success," or "Error").

Configure Allows you to edit, refresh, or remove an entry in the DDNS Entries table.

To Configure a DDNS Client

Click New. For more information on configuring a new DDNS client, see Dynamic DNS Configuration.