Jorge Martinez de Salinas

Sometimes you need to set up some service at home (e.g., a Web Server or a Mail Server). In my case, my IP address is dynamic and likely to change. You can always pay for a static IP address but there other valid solutions. For instance you can use a dynamic DNS service such as DynDNS. Service setup is easy; you have to follow these steps:

• Register an account at dyndns.org and configure a hostname (e.g., myhost.dyndns.org).
• Download the DynDNS client and configure it with your registered hostname. There are versions for Windows, Linux and Mac.

Now every time your IP address changes, the DynDNS client updates the corresponding DNS records and your services are accessible again. This mode of operation has a drawback related to DNS catching. All records in DNS have a Time to Live (TTL) value. This value dictates how long a record should be stored locally before a new copy of the record must be retrieved from DNS. Sometimes the information in DNS changes, but the old information is still stored in the DNS caches. When the cached record is different from the newest information in DNS, it is called a caching error.
DynDNS allows you to set the TTL value to 60s or 4h. If your IP is dynamic you should use the 60s value.

In summary, if availability and grade of service are key aspects for you, pay for a static IP. Otherwise you can always use services like DynDNS.