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Mire szolgál a DDNS (Dynamic Domain Name System) és hogyan lehet azt használni?
Mi a DNS?
DNS szolgáltatást (Domain Name System) az IP-címek átalakítására használják a domain névből a számszerű formátumba. Ez azt jelenti, hogy nem szükséges emlékezetben tartani a címet 62.121.128.13, elegendő megjegyezni a www.dipol.com.pl. A DNS-név fordítását a megfelelő DNS kiszolgáló hajtja végre, hogy melyik számítógépnek küldenek egy kérést, amelyik a cím fordítását kéri. Fogadtatás után a válasz a megfelelő számszerű címmel, a számítógép csatlakozik a keresett számítógépes szerverhez.

Az ügyfél diagramja - szerverkommunikáció:
1. Melyik IP-cím, ami egyenértékű www.dipol.com.pl-lal?
2. www.dipol.com.pl van a 62.121.128.13
3. Hi, 62.121.128.13 ! Küldjed a WWW tartalmat nekem.
4. Itt van ez!

Az ilyen kommunikáció akkor lehetséges, amikor a célszervernek van egy olyan statikus IP-címe, aminél ez mindig hozzáférhető. A rekord, egyszer az adatbázisba összekapcsolódik a 62.121.128.13 cím a www.dipol.com.pl-al, ahol a fenti adat mindig állandó. Ezért az ügyfél a szerverrel tud kommunikálni bármelyik domain cím is az (használja a DNS fordítást), vagy közvetlenül a numerikus cím által (a DNS szolgáltatás segítsége nélkül).
Mi a DDNS?
If we wish to run a server for website hosting or accessing CCTV camera, available from any Internet location and we don't have a static IP address but a dynamic one supplied by DHCP server (Neostrada - ADSL service in Poland is a good example of such an option), we have to use DDNS (Dynamic Domain Name System) service.
Hogyan dolgozik a DDNS?
Neostrada clients do not have a static IP - it is changed periodically. As we have shown above, in this situation it is impossible to run a server, because the current IP address of the server would have been unknown. DNS server, which translates domain name into numeric form, points at one specific IP. Once the IP number changes, the DNS data ceases to be valid.
The solution is provided by DDNS service. Similarly to DNS server, it provides a database containing relations between domain and numeric addresses, but this database may be updated on request by the domain owner. Thanks to this feature, the server is available in the domain address regardless its actual IP number. In such a case, the access to the server is limited to its domain name translated by DDNS server, unless we know its actual IP number (but of course we do not know how long it will be valid).
We have to remember that when DHCP server changes the IP, it takes some time to detect this change by the client software or router, and, after the notification is sent to DDNS server, it takes another minute or so to send this piece of data to DNS server to update the database. In result, our server will be periodically unavailable up to several minutes, every time the IP address has been changed.
DDNS in action:
1. Your IP address is 83.17.30.134
2. dipol.no-ip.org to is 83.17.30.134
3. What is current IP address of dipol.no-ip.org?
4. dipol.no-ip.org is now 83.17.55.212
5. Hi, 83.17.30.134 send me your www content
6. Here it is!
7. Your IP address has changed to 83.17.55.212
8. dipol.no-ip.org is now 83.17.55.212
9. What is the current IP of dipol.no-ip.org?
10. dipol.no-ip.org is now 83.17.55.212
11. Hi, 83.17.55.212. Send me your www content.
12. Here it is!
DDNS service is accessible via a number of providers. Its basic version, sufficient to support the above configuration, is usually free of charge. All devices supporting DDNS usually have several provider addresses preset by default. The most popular are:
DDNS configuration
To use DDNS in DynDNS service go to http://www.dyndns.org and register (the link in the upper right corner: Create Account).
Login window
In the new window enter Username, Email, Password. Mark "I agree to the acceptable use policy (AUP)" and click on Create Account - the system will inform about new account that has been prepared. To verify the account the system sends additional information to the entered email address.
DynDNS Account window
Email information
After clicking on the link with confirmation address the user signs up for this account.
Account information
The user can login and start using the account by clicking e.g. the link Create a dynamic DNS host within our Free domains:
Account confirmation
In the next window click on Get Started
Dynamic DNS page
The website will automatically display login window:
Login window
Another thing is to choose the host name and domain. After entering the information, tick Offline Hostname and click Create Host.
Creation of new host
Information on free service. Click Next.
Free Dynamic DNS Account
Once you have confirmed the contents of your cart your services will be instantly activate. - click Activate Services.
The final request
The service has been created.
Configuration of ADSL router (example: TP-LINK TD-W8910G N2901)
To perform device configuration, log on via your web browser to the ADSL router (see the Library article: Configuration of ADSL routers)
Enter the Advanced Setup/DNS/Dynamic DNS tab.
Dynamic DNS window in TP-LINK N2901
Click the Add button.
DynDNS configuration
In the next window enter:
  • D-DNS provider: DynDNS.org
  • Hostname: full name
  • Interface: interface connecting with the Internet
  • Username: name at dynDNS.org
  • Password: password to the account at dynDNS.org
Dynamic DNS settings in TP-LINK N2901
After completing the data click Add and reboot the device (Management/Reboot).
The configuration of the TP-LINK device has been done. Now, you can connect to the ADSL router via the Internet by typing the host name in the web browser.
Configuration of computer connected directly to ADSL line
If the computer is directly connected to ADSL line via a modem with USB interface, it requires to install appropriate software. It will allow for the automatic verification of the current IP address that is assigned by the DHCP server, which is located in the DDNS service. The program detects a change of IP address, reads it, and then connects to the DDNS server that provides the new, up-to-date information. To download the utility, click here.
Once installed, the program asks you to enter login and password that you created on www.dynDNS.org.
Login box
After entering the data select the previously created host in the Dynamic DNS Hosts field, and click Apply.
The main window of the program
The configuration of the program and computer has been done. Now, you can connect with the computer via the Internet by typing the host name in a web browser.