Limitations of Dynamic DNS or DDNS


Shutting down a computer or disconnecting from the network, means its IP address is assigned to the domain name. If the IP address is offline, lead connection attempts only takes place after several seconds delay to a timeout error.

As a solution approach, a client can delete the domain name at shutdown temporarily in some DDNS providers.

Another approach is the use of heartbeats in order to recognize when a computer is off-line and then removing the domain name automatically.

Dynamic DNS is not a full replacement for a static IP address. Open network connections remain in the separation from the Internet or when changing the IP address and hang collapses after a timeout.

Within the Time to Live of the DDNS entry, the old IP address needs to be cached so that no new connection can be established.

Due to immature DDNS client software, it may happen that the DDNS entry is not updated for a long time. This happens for example when the client attempts to update only once when dialing the DDNS entry, but not try again during a temporary error.

The reverse case can be problematic: a client tries to update more frequently than necessary, this is a violation of some DDNS providers Terms of Use, which may result in the suspension of an account.

This occurs for example in home routers that do not store the assigned IP address and thus send update requests on every reboot, for example, after the unplugging from the mains.

If the ISP after restarting is re-allocated the same IP address, an unnecessary DDNS update is performed. Therefore, it can sometimes take a long time until this problem is visible.

From the router, this could be prevented by the fact that this previously performs a DNS query for the domain name to be updated dynamic and determined in this way, the last used IP address.

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