非常巧妙的脚本，哪位大侠能说说原理是啥。

kzyfl

以下是PPPOE多线ddns脚本，（ros5.X）非常好用。就是不知道原理是啥，哪位大侠能帮解释解释。
Open a terminal window and paste both scripts below.
Then using the script window change the UserID, Password, and hostname.

/system script
add name=HomingBeacon policy=\
    ftp,reboot,read,write,policy,test,winbox,password,sniff,sensitive,api \
    source="# HomingBeacon Main Dynamic DNS Update Script\r\
    \n# Written by Sam Norris, ChangeIP.com\r\
    \n# 20100728 Tested on routeros 4.9\r\
    \n# 20110511 Tested on RouterOS 5.2\r\
    \n\r\
    \n# Set your specific ChangeIP.com preferences here.\r\
    \n:global ddnsuser \"USERID\"\r\
    \n:global ddnspass \"PASSWORD\"\r\
    \n:global ddnshost \"HOSTNAME.changeip.net\"\r\
    \n# Change ddnsport to 8245 to bypass proxy.\r\
    \n:local ddnsport 80\r\
    \n\r\
    \n# Do not edit anything below this line.  You have been warned.\r\
    \n# Abusive updates to the system will cause firewall blocks.\r\
    \n\r\
    \n# Please be considerate and\r\
    \n# do not let this script run more than once per 3-5 minutes.\r\
    \n\r\
    \n:log info \"DDNS: Starting.\"\r\
    \n\r\
    \n# Initialize checkpoint\r\
    \n:global ddnscheckpoint\r\
    \n:if ([:typeof \$ddnscheckpoint] = \"time\") do={\r\
    \n\t:log info (\"DDNS: Last check was \" . ([/system clock get time] - \$d\
    dnscheckpoint))\r\
    \n} else={\r\
    \n\t:log info \"DDNS: Cannot determine checkpoint, set now.\"\r\
    \n\t:global ddnscheckpoint ( [/system clock get time] - 1d )\r\
    \n}\r\
    \n\r\
    \n# Get the current IP\r\
    \n:if ([/system clock get time] - \$ddnscheckpoint > [:totime 180s] || [/s\
    ystem clock get time] - \$ddnscheckpoint < [:totime 0s]) do={\r\
    \n   :log info \"DDNS: Performing remote IP detection.\"\r\
    \n   /tool fetch address=\"ip.changeip.com\" host=\"ip.changeip.com\" src-\
    path=(\"/\?\" . [/int eth get 0 mac-address ]) dst-path=\"ip.changeip.com.\
    txt\" mode=http port=\$ddnsport\r\
    \n   :global ddnscheckpoint [/system clock get time]\r\
    \n} else={\r\
    \n   :log info \"DDNS: Please be considerate and wait a few seconds longer\
    .\"\r\
    \n   :break\r\
    \n}\r\
    \n\r\
    \n# Parse the IP address received from fetch script.\r\
    \n\t:global ddnslastip\r\
    \n\t:local html [/file get \"ip.changeip.com.txt\" contents]\r\
    \n\t:local ddnsip [:pick \$html ([:find \$html \"<!--IPADDR=\"] + 11) [:fi\
    nd \$html \"-->\"] ]\r\
    \n\r\
    \n# Is it a valid IP and is it different than the last one\?\r\
    \n\t:if ([:typeof [:toip \$ddnsip]] = \"ip\" AND \$ddnsip != \$ddnslastip \
    ) do={\r\
    \n\t\t:log info \"DDNS: Sending UPDATE with \$ddnsip\"\r\
    \n\t\t:log info [/tool dns-update name=\$ddnshost address=\$ddnsip key-nam\
    e=\$ddnsuser key=\$ddnspass ]\r\
    \n\t\t:global ddnslastip \$ddnsip\r\
    \n\t} else={\r\
    \n\t\t:log info \"DDNS: No update required.\"\r\
    \n\t}\r\
    \n}\r\
    \n"

/system scheduler
add comment="ChangeIP.com Dynamic DNS Update" \
  disabled=no \
  interval=5m name=DynamicDNS \
  on-event=HomingBeacon \
  policy=read,write start-time=startup

aboutblank

这个应该是通过 changeip 自己的一个页面来检测你访问过来的IP. 悲剧的是我这个垃圾的运营商会在对外访问时将我端口的公网地址NAT成另外一个公网地址, 此举本来应该是为了限制P2P的, 却也顺便把这个DDNS脚本给封了. 3.x时代好用的脚本5.x又不能用, 我现在正头疼这个呢

qile

运营商会在对外访问时将我端口的公网地址NAT成另外一个公网地址, 此举本来应该是为了限制P2P的, 却也顺便把这个DDNS脚本给封了