Dynamic DNS

What is Dynamic DNS

 Dynamic DNS is a technology that dynamically updates the DNS database so that you can have a global host name (domain name) even if you do not have a fixed IP address.

 With ADSL, FTTH, etc., the IP address assigned by the provider when connecting to the Internet will change if the connection is disconnected even if it is always connected.

 If the IP address changes, the integrity of the association between the domain name and the IP address cannot be maintained. In other words, if you do not acquire a fixed IP address and domain as a set, you cannot have a global host name.

 Even if you don't get a fixed IP address, you can get only a domain and rent a rental server, but you need to get a fixed IP address to publish your own Internet server.

 However, if you get a fixed IP address for yourself, the monthly cost will be ridiculous. That's where Dynamic DNS comes in handy. Most of the sites that operate Dynamic DNS operate on subdomains. in short,. If you operate it with a subdomain, you can build a site without paying a domain acquisition fee.

Below are sites that provide free Dynamic DNS services.

Site nameURLs
DHShttp://www.dhs.org/
DtDNShttp://www.dtdns.com/
Dyn DNShttp://www.dyndns.com/
my IPhttp://www.myip.org/
No-IP.comhttp://www.no-ip.com/
yi.orghttp://www.yi.org/

* The above site is a site that provides DDNS service at the time of content creation. Service is not guaranteed for the long term.

 Even if you don't have a fixed IP address, you can have a global host name, but every time your IP address changes, you need to access the site that provides the Dynamic DNS service and report it.

 It's a tedious task, but this is the fate of non-fixed IP addresses. Without this hassle, you wouldn't have a global hostname with a non-static IP address. You can't predict when your IP address will change, so you should always keep an eye on it. Being on the lookout all the time is hard work.

 There is a convenient free software called DiCE to solve this problem. By using this free software, every time your IP address changes, you will be automatically notified and registered.

 If you really want to publish your server, Dynamic DNS is not recommended. In Japan, there are still few places that provide stable services, so I think that you will use overseas sites. The free Dynamic DNS service is currently not very stable.

 Also, every time the IP address is changed, the DDNS service is notified, but there is a slight time lag, and the drawback is that it tends to be unstable during that time.

How Dynamic DNS works

Here, we will explain how Dynamic DNS works. Dynamic DNS is abbreviated as DDNS below.

Assume that the host name of the web server to be published is "xxx.dyndns.org".

① When you connect to the Internet, your ISP assigns you an IP address.

②Notify the assigned IP address to the DDNS service.

 If the IP address assigned to the router's WAN-side interface is used as the global IP address of the host to be published, it is necessary to notify the router whenever the global IP address assigned to the router changes.

 To notify, you need to register on the homepage of the site that provides the DDNS service. Assigned IP addresses can change at any time, so you should always monitor them.

 With DDNS, if you do not notify the changed IP address, the old IP address will be returned forever. This notification work is a troublesome part of DDNS.

 There is a convenient free software that automatically does this troublesome work. By using this free software, you can check the global IP address of the router periodically and automatically notify and register every time the IP address changes.

 Some recent routers have a built-in DDNS automatic update function without using tools such as DICE. In that case, it is convenient to use that function.

(3) The DDNS service updates the DNS records of the DNS server it manages.

④ A third party inquires about the IP address of "xxx.dyndns.org".

⑤ The DDNS service returns the IP address "200.200.200.200" of "xxx.dyndns.org".

The figure below shows the flow of how DDNS works.

 In DDNS, it is essential to notify us as soon as your IP address changes. If you do not notify the IP address, the host name and IP address will not be consistent no matter how long it takes, and a third party will not be able to access the server published by DDNS.

Dynamic DNS (automatic registration tool DiCE)

 With DDNS, if you do not notify the changed IP address, the old IP address will be returned forever. This notification work is a troublesome part of DDNS.

 There is a convenient free software that automatically does this troublesome work. By using this free software, you can check the global IP address of the router periodically and automatically notify and register every time the IP address changes.

 There is a tool called DiCE in free software that is easy to use. Regularly check the global IP address of the router and register the IP address if it changes.

You can download it from the link below.

http://www.hi-ho.ne.jp/yoshihiro_e/dice/

I will explain the setting procedure of the automatic update software "DiCE" of DDNS.

 Install it and start DiCE. Upon booting, the IP address of your router will be displayed to the right of the logo and in the status bar below.

Click "Event" → "Add" and register the information obtained from the DDNS site on the new event setting screen.

 Click the "IP address monitoring" tab in "Options" → "Preferences". Settings are important here. It periodically monitors the global IP address of the router with the specified numerical value. Since it is set by default, there is no problem, but if there is a problem after operating it, change it.

With DiCE, you can also see logs, so you can check later how much your global IP address has changed.