ASUS AC66U B1 to Modem instabilities

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New Around Here
Greetings fellow networking enthusiasts,

I'm experiencing an issue with my WAN interface towards my Modem of my ISP.
Let me briefly describe the topology and the issue I'm experiencing.

A while ago, I decided to make the swap from a Telenet 'HGW' to a Telenet 'Modem Only', to use more functionalities and work more efficiently.
At that time, we weren't sure whether this ASUS Router would support IPTV, which we're using here at home.
To tackle this issue, the technician who did the modem replacement advised me to place a switch between the modem and my Asus Router.
This to separate the IPTV connection from my LAN network, the IPTV cable goes from the switch directly to my modem, without passing the router.
The other LAN devices are connected from my router to the switch, which then connects it to my modem.
This all worked fine until a few weeks ago...

Since last year December (approximately), the WAN interface tends to drop now and then, at irregular intervals.
I always fixed this by either rebooting the router, or by unplugging the UTP cable, but I'm not sure if this is an L1 issue.

Now since recently I noticed that whenever the WAN interface fails, or becomes unavailable (and shows a red LED on the router itself), the corresponding port on the switch remains up, meaning that this shouldn't be a L1 issue.

After digging in the logs, and checking the GUI, I noticed the following errors (see attachments), this looks like it might be an issue related to the ISP (Telenet in this case).

Anyone has experienced the same behaviour or issues before?

PS: Another question, I tried the script in the GitHub wiki to automatically restart the WAN interface, whenever it doesn't reply to multiple pings (
However, when I reboot the router as the latest step and then check my cronjobs with 'cru l' I don't see the job in the list over there, any explanation for this?

Many thanks in advance!




  • DHCP Error GUI.png
    DHCP Error GUI.png
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  • Syslog DHCP Error.txt
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New Around Here
Extra: Telenet stated they remotely checked the modem and saw no issues, but I think they checked the modem at a time that the issues weren't occurring.
I asked them if I can contact them whenever the issue reoccurs, to validate some things at the moment itself.


Occasional Visitor
If I understand the configuration you've described, I think I see a conflict here. My first question is whether the ISP is providing two IP addresses through the modem or just one. If just one, then your IPTV device and your router are competing for it which would be a problem. But, either way, from what you're saying, you have the modem and the router and the the IPTV devices and a LAN port all plugged into the same switch. Is that right? First, to keep things simple, I'd plug the router directly into the modem, the switch into the router and all the devices -including IPTV - into the switch or directly to a LAN ort on the router. If you find that that causes problems for IPTV, and if your ISP is provides two IP addresses through the modem, then you can plug the switch into the modem and the IPTV device and router into the switch. BUT, do not plug anything else into that switch. You can plug a second switch into a LAN port on the router and your devices into that.
ASUS routers do support IPTV so look at this see if you can simplify things:

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