一、首先说明，本篇受“情灭缘尽”转帖的脚本启发，其发布的原始脚本如下：
# Dynamic DNS Update Script v1.1
# ——————————
# This script will perform automatic dynamic dns updates on the Mikrotik
# router platform. (http://www.mikrotik.com/) Since Mikrotik does not
# support sending http requests we have created a smtp -> ddns proxy service
# which will take the http URL querystring used for a dynamic dns update and
# process it via email.
# ——————————
# Written by Sam Norris, ChangeIP.com
# 7/31/04 – Created script.
# 12/9/04 – Made some values dynamic (smtp server, dhcp interface)
# ——————————
#
# Instructions:
# There are a few variables down below that you need to configure for your
# specific setup. Please modify the variables in the ‘ddnsInit’ script to
# reflect your specific information, ie userid, password, hostname to update.
#

# Blow away any existing script code, if necessary.
/system scheduler remove ddnsJob
/system script remove ddnsCheck
/system script remove ddnsInit
/system script remove ddnsReset
/system script remove ddnsSendUpdate

# Setup global variables needed to keep track of changing IP address.
/system script add name="ddnsInit" source={

:log message="ddnsInit: Creating Dynamic DNS update system."

# ENTER YOUR CHANGEIP.COM USER ID HERE.
:global u
:set u "USERID"

# ENTER YOUR CHANGEIP.COM PASSWORD HERE.
:global p
:set p "PASSWORD"

:global s
:set s "Mikrotik"

# ENTER THE TARGET HOSTNAME TO UPDATE, *1 is Set 1.
:global h
:set h "*1"

:global dhcpInterface
:set dhcpInterface [ /ip dhcp-client get interface ]
:log message=("ddnsInit: Found dhcp interface " . $dhcpInterface )

# EMAIL PROXY ADDRESS – DO NOT CHANGE FOR PRODUCTION.
:global ddnsProxyEmail
:set ddnsProxyEmail "ddnsUpdate@ChangeIP.com"

# ENTER YOUR EMAIL ADDRESS FOR CONFIRMATIONS.
:global ddnsFromEmail
:set ddnsFromEmail "youremail@domain.tld"

# SMTP DDNS PROXY SERVER – CHANGE ONLY IF NECESSARY (port 25 blocked?)
:global ddnsSmtpServer
:set ddnsSmtpServer [:resolve smtp.changeip.com]

:global a
:set a [ \
/ip address get \
[/ip address find interface=$dhcpInterface] \
address \
]

}

/system script add name="ddnsCheck" source={
:if ([/system scheduler get ddnsJob run-count]<=1) do={
/system script run ddnsInit
}
:global temp
:global b
:set temp $a
:set b [ \
/ip address get \
[/ip address find interface=$dhcpInterface] \
address \
]
:if ($temp != $b) do={
:log message="ddnsCheck: Found new IP address."
/system script run ddnsSendUpdate
:set a $b
}
}

/system script add name="ddnsSendUpdate" source={
:log message=("ddnsSendUpdate: Sending Dynamic DNS smtp update to " . $ddnsSmtpServer)
/tool e-mail send \
to=$ddnsProxyEmail \
from=$ddnsFromEmail \
server=$ddnsSmtpServer \
subject="New Dynamic IP" \
body=("u=" . $u . "&p=" . $p . "&hostname=" . $h . "&system=" . $s . "&myip=" . $b)
}

/system script add name="ddnsReset" source={

:log message="ddnsReset: Resetting global values."
/system scheduler set ddnsJob run-count=0
:unset u
:unset p
:unset s
:unset h
:unset dhcpInterface
:unset ddnsProxyEmail
:unset ddnsFromEmail
:unset ddnsSmtpServer
:unset a
:unset b
:unset temp

}

/system scheduler add name=ddnsJob interval=30s on-event=ddnsCheck

二、红色部分是需要根据个人注册的信息填写

三、黄色部分是我要着重解释的，也是成功的关键。

四、具体说明：
1、该脚本是基于www.changeip.com网站申请的免费动态域名，大家可自行申请；
2、该脚本的原始作者sam norris就是www.changsip.com的运行者，故此，这个脚本在ros下是绝对支持www.changeip.com申请的域名，至于其他国内的类似www.3322.org等我还没有试过，不知可不可以
；
3、
:global dhcpInterface
:set dhcpInterface [ /ip dhcp-client get interface ]
:log message=("ddnsInit: Found dhcp interface " . $dhcpInterface )
这是本文的关键部分，sam norris是基于dhcp客户机的架构来设置他的动态域名，而国内用户主要关心的是adsl拨号下得动态域名解析，dhcinterface是一个全局变量，他代表的是dhcp客户机的接口号，也就是分到ip地址的接口设备名，这个变量名可以不改，但如何取得你的系统中adsl设备的接口号呢？请将 [/ip dhcp-client get interface] 改为 [/interface find type=pppoe-out],好了，dhcpinterface的值就变成了你所建立的adsl拨号接口号了，ros内部的表示一般为*3，当然这个不用关心。至此，你所要做的就是等待了；

4、关于脚本的建立我在此就不多说了，大家只要把上述脚本的各个部分复制-粘帖到命令交互界面，自然会生成，正确的结果是生成四个脚本，分别为： ddnsCheck,ddnsInit,ddnsReset,ddnsSendUpdate;同时生成一个名字为ddnsJob的计划日程。

最后祝大家成功，ros自己能做的事情自己做，从此摆脱ros+windows +域名客户软件的日子。