Modecom MC-4220 User Manual page 73

to register with some website and get a domain name. When the IP address of the
host changes, it just needs to send a message to the website that's providing dynam-
ic DNS service to this host. For this to work, an automated update client needs to be
implemented. These update clients send update messages to the servers whenever
there is some change in the IP address of that host. Then, the server updates the
entries for that host and replies back with some return code.
Above Figure explains one such scenario in which a host gets a dynamic IP ad-
dress for itself from a DHCP server. As the host has registered with one of the dy-
namic DNS service providers on the Internet, it sends an update message to the ser-
vice provider with host name and changed IP address. The service provider updates
the new IP address of the host in the zone files that have entry for that host name
and replies back with some return code. The return code communicates the success
or failure of the update message. This process is repeated every time the host's IP
address changes.
If the dynamic DNS service provider is notified of the same IP address again and
again, then it considers it an abuse and might block the host name. To avoid this
scenario, the IP address that was successfully updated to the ISP is stored on the
unit. Whenever we receive an IP address change notification, the new IP address is
compared with the IP address that was stored on the last update. If they differ, then
only an update request is sent. However, when the system comes up there is no way
of knowing what was the IP address on last successful update before the system
went down. You need to give the command "system config save" periodically to save
this IP address on Flash.
Registering With Dynamic DNS Service Provider
Currently, Wireless ADSL2+ Router supports two Dynamic DNS service providers,
www.tzo.com and www.dyndns.com. To use their Dynamic DNS service, you first
need to visit the Web site of a service provider and register. While registering, you
need to provide your username, password, and hostname as mandatory parameters.
A service provider may also prompt you to fill some optional parameters.
802.11n WLAN ADSL2+ Router
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