User manual

3.7. Dynamic DNS Settings
A DNS feature offered by NetDefendOS is the ability to explicitly inform DNS servers when the
external IP address of the DFL-160 has changed. This is sometimes referred to as Dynamic DNS
(DDNS) and is useful where the DFL-160 has an external IP address that can change.
By enabling this option, NetDefendOS acts as a dynamic DNS client and every time it restarts, it
will send a message so the dynamic DNS server is informed of the current IP address on the WAN
interface. This messaging is also repeated at set intervals during normal operation.
The httpposter CLI Command
The CLI console command httpposter can be used to troubleshoot problems by showing what
NetDefendOS is sending and what a server is returning during dynamic DNS lookup.
All CLI commands are documented in Appendix A, CLI Reference.
Usage in VPN Scenarios
Dynamic DNS can also be useful in VPN scenarios where both ends of the tunnel have dynamic IP
addresses. If only one side of the tunnel has a dynamic address then the NetDefendOS VPN keep
alive feature solves this problem.
Note
Dynamic DNS services are often sensitive to repeated logon attempt over short periods
of time and may blacklist IP addresses that are sending excessive requests. It is
therefore not advisable to query these services too often otherwise they may cease to
respond.
The D-Link DDNS Server
D-Link offers its own DDNS server which is a free service for D-Link customers. Registration is
required and can be done by going to https://www.dlinkddns.com/login. This service is
recommended but one of the other pre-defined services could be used instead.
3.7. Dynamic DNS Settings Chapter 3. The System Menu
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