H3C Technologies H3C SecPath F1000-E - Manual (Page 256)

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Configuring DDNS
Overview
Although DNS allows you to access nodes in networks using their domain names, it provides only the
static mappings between domain names and IP addresses. When you use the domain name to access
a node whose IP address has changed, your access will fail because DNS leads you to the IP address
that is no longer where the node resides.
Dynamic Domain Name System (DDNS) can dynamically update the mappings between domain names
and IP addresses for DNS servers to direct you to the latest IP address corresponding to a domain name.
Figure 141 DDNS networking application
As shown in Figure 141 , DDNS works on the client-server model.
• DDNS client—A device that needs to update the mapping between the domain name and the IP
address dynamically. An Internet user usually uses a domain name to access the server providing
application layer services, such as an HTTP server or an FTP server. When its IP address changes,
the application layer server runs as a DDNS client that sends a request to the DDNS server for
updating the mapping between the domain name and the IP address.
• DDNS server—Informs the DNS server of latest mappings. When receiving the mapping update
request from a DDNS client, the DDNS server tells the DNS server to re-map between the domain
name and IP address of the DDNS client. Therefore, the Internet users can use the same domain
name to access the DDNS client even if the IP address of the DDNS client has changed.
NOTE:
•
At present, the DDNS update process does not have a unified standard and depends on the DDNS
server that the DDNS client contacts. The well-known DDNS service providers include www.3322.org,
www.oray.cn (also known as the PeanutHull server), and www.dyndns.com.
• With the DDNS client configured, a device can dynamically update the latest mapping between its
domain name and IP address on the DNS server through DDNS servers at www.3322.org or
www.oray.cn for example.