Use DDCLIENT under Mac-Snow Leopard 10.6 and just with DYNU.COM with domain already is made...
if you have a static or named fixed ip - you do not need updater... read down for manual update.
ddclient is offered for auto updater on dynamic ip on period time...

Install the App

Run in Terminal app:
past-> ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"
and press enter/return key if need password - enter... Wait all to finish.
past-> brew install ddclient

is not ready yet!

You can see the path on ddclient.
config file -> /user/local/etc/ddclent/ddclient.conf
App path -> /user/local/Cellar/ddclient/3.8.3/sbin/ddclient
App folder -> /user/local/Cellar/ddclient/3.8.3/
App cache -> /user/local/var/run/ddclient/ddclient.cache
alias
App path -> /user/local/opt/ddclient -> point to folder name - 3.8.3
App path -> /user/local/sbin/ddclient -> point direct to app

edit app - config file with text edit program and save to location up...

daemon=60 # Comment this line for OS X
syslog=yes # Log update msgs to syslog.
mail=root # Mail all msgs to root.
mail-failure=root # Mail failed update msgs to root.
cache=/usr/local/var/run/ddclient/ddclient.cache # record Cache in file.
pid=/usr/local/var/run/ddclient/ddclient.pid # record pid in file.
use=web, web=checkip.dynu.com/, web-skip='IP Address' # Get ip from server.
server=api.dynu.com # IP update server.
protocol=dyndns2
login=LOGIN-name # your username.
password=LOGIN-password # your password.
domain-name.com # update IP for domain name and alias.
www.domain-name.com # alias must to be set

make a plist file for start on boot
use text edit program and sve to path: /Library/LaunchDaemons/org.ddclient.plist
*** down text select - copy past to editor and save under name - org.ddclient.plist
----start down-line
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
<key>Label</key>
<string>org.ddclient</string>
<key>OnDemand</key>
<true/>
<key>ProgramArguments</key>
<array>
<string>/usr/local/Cellar/ddclient/3.8.3/sbin/ddclient</string>
<string>-file</string>
<string>/usr/local/etc/ddclient/ddclient.conf</string>
</array>
<key>RunAtLoad</key>
<true/>
<key>StartCalendarInterval</key>
<dict>
<key>Minute</key>
<integer>0</integer>
</dict>
<key>WatchPaths</key>
<array>
<string>/usr/local/etc/ddclient</string>
</array>
<key>WorkingDirectory</key>
<string>/usr/local/etc/ddclient</string>
</dict>
</plist>
----- end up-line
set permissions to system(is root)=read/write - must to be set manual

TEST begin in terminal

force update real test
sudo /usr/local/opt/ddclient/sbin/ddclient -force -debug -verbose -noquiet

check log file
tail -f /var/log/system.log

check plist do is work - first load in memory
sudo launchctl load /Library/LaunchDaemons/org.ddclient.plist

if -> org.ddclient <- exist in list is nice
sudo launchctl list

Restart the MODEM and he must to get new IP
Restart the computer and the host must to exist in browser

But if the host not exist in browser
*** MAKE MANUAL UPDATE is possible from web site Dynu.com
steps:
Login by form
DDNS Service click on icon
Actions click on pencil
on corner right on web page is your ip now select and with keyboard keys make a copy
select ip shown-recorded in the form on left and with keyboard keys make a past
SAVE the form click on green button
that is a manual ip update
check the host now ....

DONE must all to be good now


Please, if you have a notes PLEASE posted them...
Thanks