DYNDNS.TXT 19/10/03

			 Dynamic DNS Update Client
			 =========================

More and more people these days have dynamic IP addresses, i.e. IP
addresses which are assigned by their Internet Service Provider and
which may be different each time they log on.  Broadband users are
permanently connected to the internet, but even their IP addresses
may be changed at any time by the ISP, unless they pay extra for a
static address.

For the normal internet user this is not a problem, because no-one
else needs to know their IP address. However, if you want other people
to be able to connect to your system, e.g. if you are running a web
server, they need to know your current IP address. This is where the
dynamic DNS providers come in.

There are many organisations providing dynamic DNS services, one of
whom is DYNDNS.ORG. It is easy, and free, to set up an account with
dyndns.org, and after doing so you may choose one or more hostnames
for your system. For example, the hostname for my router is
"g8pzt.ath.cx". All you then have to do is keep dyndns.org informed
of your current IP address, either manually or using an automatic
update client. Whenever someone asks their system to connect to
"g8pzt.ath.cx", they will be given my current IP address.

From version 184a, Xrouter has an integral client for automatically
maintaining dynamic DNS entries at dyndns.org, thus obviating the
need to run an external client or perform manual updates.  If the
client is enabled, and your IP address changes, it will update one
or more hostname entries on the dyndns.org DNS server.  If you do not
use dynamic dns, you need read no further.

The client is enabled by including the directive DYNDNS=1 in relevant
PORT configuration block in XROUTER.CFG, i.e. the port which is
connected to the Internet. DYNDNS=0 disables the client, as does
omitting the directive altogether. Note: you must only use this
directive on ONE port, and you may crash Xrouter if you try to use it
on more than one.

The client requires a configuration file, DYNDNS.CFG, and it creates
a data file DYNDNS.BIN. The configuration file contains plenty of
comments, so it should be self-explanatory.

If your Xrouter is *directly* connected to the Internet, i.e. via a
PSTN modem or non-routing cable modem, the client simply monitors
the port IP address (which is assigned by the ISP using IPCP or DHCP),
and tells dyndns.org when it changes. This mode is selected by putting
"NO" on the "Use external IP detection service" configuration line in
DYNDNS.CFG.

However, if your connection to the Internet is via a NAT router such
as an ADSL modem/router or Windows ICS, the port IP address will be
a "private" one which no-one else could access. In this case, the
client can be configured to query an external IP address detection
service at regular intervals, updating dyndns.org if a change is
detected. This mode is selected by putting "YES" on the "Use external
IP detection service" configuration line.

Free accounts on dyndns.org are removed if they haven't been updated
for 35 days. Thus, if your IP address hasn't changed for 30 days, the
client automatically sends an update to keep the account refreshed.

You may have more than one hostname associated with your IP address,
but that's not a problem. In the "hostname(s) to be updated" line,
simply list the hostname, separated by commas. Be careful not to
include any spaces or mistakes in the line.

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