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FAQ > Technical

1. How often can/should I update my IP address ?
    can: You cannot update your IP address more than one time every 5 minutes.
    should: Normal client behaviour is to update your IP address only when it changes. You are supposed to keep a local copy of the IP address you last updated to compare your current IP address with.
    Updating your IP address on fixed intervals is not allowed.
2. After I updated my IP address, does my hostname resolve directly to my new IP ?
    Our SOA records intruct DNS caches to cache your records for 5 minutes. So in the very worst case, it takes 5 minutes for your IP to reach the whole world.
    In the average case, your update will be effective after 15 seconds.
3. I cannot accept HTTP connections, can I run a webserver using DyNS services?
    Yes, you can.
    There is a hosttype defined for this purpose; a Dynamic Forwarder. You can update this host with your client programs, and have the incoming HTTP requests redirected to any port you choose.
    Be sure not to violate your provider's AUP when using this service.
4. Cool, I'd like to write my own client now, where do I start ?
    Read the technical documentation. It contains the protocol specifications and guidelines for writing and testing your own clients.
    We're always interrested in hearing from people who wrote their own client.
    There is also a DyNS client development forum which you might find useful to get in contact with fellow-developers.
5. Can I have my IP address reverse resolved to my hostname ?
    Not possible. Your ISP controls the reverse delegation for your IP address. There's nothing we can do about it.
    In case you ask yourself what this means, here's an example:
    myhost.dyns.net resolves to 231.41.141.113
    231.41.141.113 resolves to reserved-multicast-range-NOT-delegated.example.com and NOT to myhost.dyns.net
6. My HTTP requests go trough a Proxy server. Can I still correctly update my IP address. 7. I'd like to do fancy things with javascript in my cloaked URL forwarder. How ?
    Cloaking opens a full size frame in your browser. We called this frame 'main'. You can access the frame with this name.
8. What DNS server software don't you use ?
    We don't use BIND, the Buggy Internet Name Daemon.
    BIND is just too bloated and error-prone to run this kind of service distributed over different backbones.
    We use proprietary software to answer your DNS queries and to keep them syncronised over the different DNS servers.
    We will release the source code of our server systems when we feel it's ready to be published.
9. What's the maximal lenght of hostnames / domain names I can register ?
    Hostnames can be up to 63 characters.
    Domains can be up to 67 characters.
    So the maximal hostname site you could register is 130 characters long.
    Here's an example of this absurd length:
    hhhhhhhhhhhoooooooossssssstttttttttttnnnnnnnaaaaammmeeeeeeeeee.dddddddddooooooooommmmmmmmmmmmmmmmmmaaaaaaaaaaaiiiiiiiinnnnnnn.com
    Stupid eh ;-) , but it's possible.
10. I use ppp (pppOE) on a Linux box. How can I update my IP every time I connect ?
    First of all - install ez-ipupdate. Then procees with these steps:
    • create the file /etc/ppp/ip-up is it doesn't exist
    • At the bottom of this file, add the following line:
      /usr/local/bin/ez-ipupdate -s dyns.cx -a $4 -h YOURNAME.DYNS.CX -Sdyns -uUSERNAME:PASSWORD
      Where you fill in the capitalized words with your own information.
    • Make sure you change the permissions of this file to '-rwxr--r--' with the command 'chmod 744 /etc/ppp/ip-up'
    • The ip-up script is invoked every time your connection comes up - so also when your IP changes.
11. I am forced use a proxy and I use ez-ipupdate. can this be done ?

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