Asuswrt-Merlin custom DDNS and DDNS-START script

[H225flyer]

Hi there,

I have an Asus RT-N66U (with the latest Asuswrt-Merlin firmware) router that is running behind my new ISP's Huawei HG8247H (ONT) router/modem.
As the router module of the HG8247H is notoriously buggy (and I also wanted to use the RT-N66U’s VPN service) I am running it in bridge mode.
Everything is working well except my DYNDNS service which is updated with an incorrect ip.
The public ip assigned to the RT-N66U by my ISP is normally in the range of 100.70.xxx.xxx while my real public ip is 124.122.xxx.xxx
After more troubleshooting I found out that my ISP is running a carrier grade NAT service which explain the problem.

My service provider understand the issue and are willing to temporarily remove me from their NAT however they told me that unfortunately I would be most likely put back automatically every time they make an update/upgrade.
To save me this trouble I am now trying to use the “DDNS-START” script to update DYNDNS with a correct ip instead.
My first script (I am a newbie in sh scripting) is running (confirmed by the log) however the wget doesn’t seems to receive any argument back from DYNDNS, and as a result the update fail.

Can someone help me with issue please?

Here is my script:

#!/bin/sh
#

username=xxxxxxxxx
password=xxxxxxxxx
hostname=xxxxxxx.dyndns.org

IP=$(wget -O - -q http://myip.dnsomatic.com/)

URL="http://$username:$password@members.dns.org/nic/update?hostname=$hostname&myip=$IP&wildcard=NOCHG&mx=NOCHG&backmx=NOCHG"

logger "wan ip:"
logger $IP

ANSWER=$(wget --no-check-update -q "$URL")

logger "ANSWER"
logger $ANSWER

if ["$ANSWER" == "good"]||["$ANSWER" == "nochg"]; then
/sbin/ddns_custom_updated 1
else
/sbin/ddns_custom_updated 0
fi


Thanks!