A common issue people have when using dynamic DNS clients is how to test if they’re really working. Do you have to wait until your public IP address expires and a new one is re issued by DHCP?

Well the answer to this question is most definitely NO! Using the free PPTP VPN service from www.pptpvpn.biz you can force your public IP address to change on demand. You MUST make sure that all traffic is routed down the VPN for this to work. This is the default setting for most common platforms.

Follow these simple steps to prove for certain that your client is working.

1.) Configure your VPN

Your DNSdynamic email address and password will work with www.pptpvpn.biz. To setup your VPN log in to www.pptpvpn.biz NS obtain your VPN credentials. Then follow one of the guides linked from www.pptpvpn.biz/help.php to configure the VPN on your platform.

2.) Check your public IP address

Now start up your Dynamic DNS client, and then visit the web page myip.dnsdynamic.org to check what your public IP address is.

3.) Check your DNSdynamic domain is resolving

You can now use an online DNS lookup tool to check that your registered domain correctly points to your public IP address. A nice and easy tool can be found here;

http://www.mxtoolbox.com/DNSLookup.aspx

4.) Change you public IP address

Now to force your public IP address to change, which will trigger your dynamic DNS client to update DNS, sign in to the PPTP VPN.

5.) Check you have a different public IP address

You can now check your public IP address again from  myip.dnsdynamic.org you should observe it is now different. It will be displaying the IP address of the VPN server.

6.) Check that DNS is resolving to your new public IP address

Again using the same DNS lookup tool as in step 3 check that DNS was updated and that it now points to your new IP address.

7.) Disconnect from the VPN

Now disconnect from the VPN, after 60 seconds your domain should be updated again to point back to your original ( and current ) public IP address.

ddclient is an excellent free perl dynamic DNS client that can be used to keep your DNS hostname updated with your current public IP. If you have a dynamic IP from your ISP, using ddclient can let you run a web server on your connection and make sure that DNS is always kept up to date with your current IP address.

DNSdynamic supports the dyndns2 protocol that ddclient can be configured to use. Configuration is simple, if you have created your DNSdynamic account and have created your domain you can use the following ddclient.conf to keep your IP updated.

daemon=60                               # check every 300 seconds
syslog=yes                              # log update msgs to syslog
mail=root                               # mail all msgs to root
mail-failure=root                       # mail failed update msgs to root
pid=/var/run/ddclient.pid               # record PID in file.
ssl=yes                                 # use ssl-support.  Works with
# ssl-library
use=web, web=myip.dnsdynamic.com        # get ip from server.
server=www.dnsdynamic.org               # default server
login=user@gmail.com                # default login
password=password              # default password
server=www.dnsdynamic.org,              \
protocol=dyndns2                        \
awesome.dnsdynamic.com

You should replace the login, password settings with your own email and password that you have created at DNSdynamic. You also need to change the last line in the config file which is the domain that you would like kept up to date. Good luck, if you need any support please feel free to contact us!

Ever needed to create firewall rules for hosts using dynamic DNS, or hosts that use dynamic IP? Most howto guides walk through using a shell script and doing DNS lookups using dig +short. Now this can work for a small number of hosts, but what if you have a hundred, a thousand, or even ten thousand?

Resolving 100 hosts using dig in a for loop is going to take 20 seconds on a good day. Most dynamic dns providers use a 60 second TTL so it is necessary to generate firewall rules as fast as possible, using dig does not achieve this.

Enter Perl and the Net::DNS::Resolver module. This awesome Perl module exposes a method called bgsend. Bgsend allows you to fire off a DNS query and move onto the next piece of work without having to wait for a response. For each query it creates an IO::Socket::INET object which can then be polled using the bgisready method to determine if a response has occured.

#is it ready
if($res->bgisready($socket)) {
    my $packet = $res->bgread($socket);
    return $packet;
} else {
    return 0;
}

Using Perl and Net::DNS::Resolver it is possible to resolve hundreds of hosts in just a few seconds. Its the perfect tool to use for generating dynamic firewall rules. However there is one slight downside to Net::DNS::Resolver (of course there would be!). You can’t exactly tell the difference between NXDOMAIN and a DNS request timeout using bgsend. If a nameserver has responded with NXDOMAIN Net::DNS::Resolver leaves the IO::Socket::INET object undef.

DNSdynamic have put together a sample perl script that you can download and start to use. There are a few variables that you need to set, like the ports, the timeout, and the chain name. You will also need to create a file called hosts.allow.txt that has one host per line that you would like to create a firewall rule for. The script generates the file dynamic.iptables. You could cron the script to run every minute then flush the dnsdynamic (or whatever you have called it)  chain and then run the dynamic.iptables to bring in the new rules, keeping your firewall rules bang up to date. Of course relying on DNS to IP resolution for security is not the greatest thing to do, but sometimes its neccassery!

dyn_firewall.pl

  1.) Give your (or someone elses) DSL/ADSL/Cable internet connection a memorable name.

2.) Make a super long cool domain name.. super.long.cool.domain.name.dnsdynamic.com

3.) Run a web server at home, then test it from the internet using our free VPN service.

4.) Save money and use one of our free domains!

5.) Run a VoIP PBX from home.

6.) Give your internal hosts DNS entries.. xbox.ns360.info -> 192.168.1.3

7.) Create firewall rules for dynamic hosts.

8.) Create one off domains.. happy.birthday.mom.user32.com

9.) Get a static IP using the free VPN.

10.) Give everything a hostname!.. fridge.dnsapi.info

Have you ever needed to fetch your public IP address in a script or through some automated tool? Well DNSdynamic provides a real simple way for you to do this. Each of our available domains has the hostname “myip” registered and configured so that it always returns your public IPv4 address. Currently these URLs all work;

myip.dnsdynamic.org

myip.dnsdynamic.com

myip.dnsdynamic.net

myip.dnsd.info

myip.ns360.info

Using Bash a simple example of using this would look like;

#!/bin/bash

myip=`curl -s http://myip.dnsdynamic.org`

echo "Your IP is ${myip}"

Using Perl a simple example to fetch your IPv4 address using the LWP::Simple module would look like;

#!/usr/bin/perl
use LWP::Simple;
use strict;

my $myip = get("http://myip.dnsdynamic.org");

die "Error!" unless defined $myip;

print "Your IP is $myip\n";

Finally using Microsoft Visual Basic you can fetch your IPv4 address using the following code;

Dim sURL As String
sURL = "http://myip.dnsdynamic.org"

Dim wrGETURL As WebRequest
wrGETURL = WebRequest.Create(sURL)

Dim objStream As Stream
objStream = wrGETURL.GetResponse.GetResponseStream()

Dim objReader As New StreamReader(objStream)
Dim sLine As String = ""
Dim i As Integer = 0

Do While Not sLine is Nothing
    i += 1
    sLine = objReader.ReadLine
    If Not sLine Is Nothing Then
        MsgBox(sLine)
    End If
Loop

We hope this service is useful, need free dynamic DNS? Signup today