Appendix A: Operation Without A Static Ip Address Using Dyndns - NewMar SPM-200 Installation & Operation Manual

8.0 Appendix A: Operation Without a Static IP Address Using DynDNS

If you want to access your SPM-200 over the public Internet, your browser needs to know the unit's unique IP
address. But it can be difficult to obtain a permanent "static" IP address in many situations.
Regular Internet servers have static IP addresses. A service called Domain Name Service ("DNS") translates
the familiar names like www.newmarpower.com into its corresponding IP address (192.220.29.161).
Newmarpower.com always has that IP address, so anyone can access it from anywhere on the web.
For a home or small office installation, Internet service is provided by a telephone or cable company using
a DSL modem or a cable modem. The modem is connected to the Linksys router using 10baseT or 100baseT
Ethernet. Local machines including the SPM are in turn connected to the router using Ethernet as well.
FIGURE 22: Local Network and Router
The local machines, including the local port of the router, are assigned addresses in a private domain such as
192.168.123.XXX. The external port is assigned a dynamic address by the Internet provider's Distributed Host
Configuration Protocol (DHCP) server.
The dynamic IP address works fine for most typical applications that might be run in a home or small office
environment, such as web surfing or checking email, but it presents a problem when using a server, such as
the SPM. If people want to connect to the server/SPM from somewhere on the public Internet they need to
know an IP address that they can use to reach it. Normally they find this address using the Internet's Domain
Name Service (DNS). But if our server's address changes whenever the DHCP server changes it, then the
regular DNS service can't keep up with it.
www.dyndns.com offers a service that will solve this problem. What DynDNS does is allow you establish a
URL in one of their domains, and they keep up with changes to your IP address. Your URL is something like
www.myUrl.dyndns.biz. When you enter that into a browser DynDNS redirects the request to your current
IP address. In order for this to work you have to have a client program on your device that updates DynDNS
whenever your provider changes your IP address.
In the local network example, you want to be able to reach the SPM's Web Server from the public Internet.
There are two issues:
1) The SPM-200 is behind a local router, and has an "unrouteable" IP address.
2) The IP address of the router is assigned by the Internet Provider's DHCP server, and thus may change
without warning.
P.O. Box 1306
Newport Beach
California 92663
Phone: 714-751-0488
Fax: 714-957-1621
E-Mail: techservice@newmarpower.com
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