Netplus ZTE F670L - Internet drop issue when idle

[Static_IP]

Hi everyone, I switched to Netplus three days ago. The speeds are great, but I’ve hit a roadblock that I’m trying to solve.

The Problem:The internet works perfectly as long as I am actively using it. However, if the router sits idle for about 1–2 hours, the internet just stops. All lights on the router remain Green, but no device can access the web. A restart fixes it every time, but the cycle repeats.

ONT Model: ZTE F670L [2020 manufacturing ], Firmware Version: V1.1.20P11N1B

Findings from the Logs: I’ve been checking the router logs to see what’s happening, and I found some very specific errors that repeat thousands of times:

1. Watchdog Errors :[Informational] user regist watchdog: Monitor open device error No such device or address This occurs every 15 seconds. It looks like the internal system is failing to poll its own hardware.
2. VOIP Critical Loop :[Critical] VIP_VOIP: Set VoIP Protocol SIP This error is flooding the logs. I don't use a landline, but the router seems stuck in a loop trying to configure the VOIP service.
3. DHCP Lease Failure (3600s Lease):The WAN lease is set to exactly 3600 seconds (1 hour). Right when the internet drops, I see these events in the log:
   
   • rcv EV_T1_EXPIRED on BOUND
   • rcv EV_SEND_TIME_OUT on RENEWING
   • rcv EV_T_EXPIRED on REBOUNDING

It seems like because of all the watchdog and VOIP loops, the router gets "stuck" and fails to renew the 1-hour lease when it's idle. Once the lease hits zero, the session dies.

Questions for the experts:

• Is this a known firmware bug with the ZTE F670L on Netplus?
• How to get admin access.
• Is there any way to increase the WAN lease time? My router is heavily restricted and I only have basic 'user' access, not 'admin' access, so I can't see many settings.

 

[tr1k0N4]

Get your own equipment and throw theirs in the bin‍
And enjoy life!!

 

[Static_IP]

Hi everyone, just wanted to give an update on this.

Netplus technicians came out to diagnose the issue. When they checked my fiber line, the power was reading -16 dBm. They actually tried to reduce the power to -22 to -23 dBm by putting a small macro-bend in the fiber cord. It worked flawlessly for two days, but then the idle dropping issue returned.

To fix it, they have now upgraded me to a new router: the GX Titanium E20 (Earth 2022 model).

The Current Situation:

• The Good: Overall performance is much better, and I’ve noticed a significant improvement in the 2.4GHz Wi-Fi band stability.
• The Bad: The main problem isn't completely gone. If the network is left completely idle for a while, I am still facing that exact same old issue where the internet drops out.

The Google Home "Heartbeat" Workaround:

I stumbled upon a temporary fix by accident. I connected my Google Home Mini to the network, and as long as it is powered on, the internet never drops. Because the Google Home constantly sends out tiny "heartbeat" pings to Google's servers every few seconds, it keeps the network active. With this continuous background traffic, everything works flawlessly.

New Findings & Confusion (PON Rx Power vs. Config):

While monitoring the new router, I noticed the PON Rx Power is currently reading -14.90 dBm (likely because the fiber line unbent itself a bit over time).

This leaves me incredibly confused about the root cause:

1. Is it a Fiber Power Issue? I read online that these ONTs support an optical Rx range between -8 dBm and -25 dBm, making my -14.90 dBm technically "excellent." Yet, the technicians specifically tried to lower it.
2. Is it a Router/ISP Configuration Issue? The fact that a tiny bit of background pinging from a Google Home Mini completely stops the crash strongly points toward an idle timeout or DHCP lease renewal failure (similar to the 1-hour lease loops I saw on the old ZTE router).

Could a high signal strength like -14.90 dBm somehow cause drops only when the router goes idle? Or does this Google Home workaround prove it's 100% a routing/firmware bug on Netplus's end? Would love to get your thoughts!