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14.1.2.3-J
Dynamic DNS
With dynamic DNS it is possible to address a device which it is connected to the Internet
with a dynamic IP address. Using this feature with SX-GATE, you can get access to
the services offered by SX-GATE despite of its dynamic IP address.
Of course it is not possible to access SX-GATE from the Internet
if the dial-up link is offline. Also SX-GATE must be assigned a
"valid" Internet IP, i.e. it must not be situated behind an upstream
NAT router.
With dynamic DNS, ordinary hostnames (fully qualified domain names, FQDN) are
used to address SX-GATE. This hostname will resolve to the current dynamic IP of SX-
GATE. To enable this, SX-GATE has to update its dynamic DNS record everytime a
new dial-up connection is established.
After the update it can take a few seconds or even minutes until
the DNS name resolves to the new dynamic IP address. This is
because the DNS servers used to resolve the hostname might
have cached the old entry. The maximum period of time (Time
To Live, TTL) the DNS record can be cached is configured by the
dynamic DNS provider. Please refer to the provider for further
information.
Dynamic DNS is offered by many different providers. Some offer this service for free,
others charge for it.
Protocol
Unfortunately there's no standard protocol for updating dynamic DNS records. SX-
GATE offers a bunch of different protocols. Please consult your dynamic DNS provider,
which protocol is used and if SX-GATE supports it.
Update server of the DNS provider
Here you have to specify the server which accepts and processes the IP address
update messages. This server may be different to the webserver of the dynamic DNS
provider.
Update URL
Here you have to specify the update URL (aka "direct URL") for updating the dynamic
IP address. The URL may have the placeholders <host>, <ipaddr>, <username> and
<password> that will be substituted by the dynamic DNS name, the IP address, the
