Each evening 23.16h internet is broken for approx. a minute

Installing and Using OpenWrt
1

25.12.2 on a Cudy WR3000.

Since a few days (maybe after update to 25.12.2?) I am facing a strange issue.
Exactly at 23.16h each evening the internet access is broken.
I noticed it during streaming TV and really it is exactly the same time each evening.
I didn’t change settings during the last weeks the only change was the system upgrade.

How can I check maybe using the log what is happening here, or does somebody have an idea what might be the culprit?

Yesterday evening before 23.16h I restarted the Internet router and also the OpenWRT router but again at 23.16h internet broken for approx a minute…

2

Have you checked whether the issue at 23:16 affects all devices on your network, or only a specific client?

For example:

  • If it happens on all devices, it might be something on the router side (WAN reconnect, DHCP lease renewal, cron job, PPPoE, etc.)

  • If it only affects a single device, it could be a local issue (Wi-Fi, network settings, application, etc.)

If possible, try running a continuous ping (e.g. to 8.8.8.8) from multiple devices before and during that time to see where the connection drops.

3

First guess would be upstream ISP's "force a reconnect at every 24 hours" type of thing. Check the logs at the "internet router".

Some examples of that found with https://www.google.com/search?q=ISP+force+a+reconnect+at+every+24+hours

Check your "internet router" if it has a setting to force a reconnect during night, e.g. at 04:00.

4

The internet is lost “centrally” means at the OpenWRT router.
Also mobile doesn’t get internet during that one minute.

I will check the Zyxel router (5G mobile net) if there is a log what shows me something.
But what could I check in OpenWRT log - How and What?

5

I will check now the Zycel internet router, and I will open the 2.4 Wlan there, and check when internet drops at 23.16h if the Zyxel is also down, but again I didn't change any settings and this issue appears approx. since a week.

6

Given that the outage happens exactly at 23:16 every day and affects all devices (including those not directly tied to OpenWrt), this strongly points to an upstream event rather than something inside OpenWrt itself.

At this stage, the most likely cause is a forced reconnect or lease renewal from the ISP, which is quite common on mobile/5G connections.

To narrow it down further, I would suggest:

  1. Bypass OpenWrt completely
    Connect a device directly to the Zyxel router (via Wi-Fi or cable) and check if the drop still occurs at 23:16.

    • If yes → the issue is definitely upstream (ISP or Zyxel)

    • If no → then we can look deeper into OpenWrt

  2. Check Zyxel logs around 23:16
    Look for entries like:

    • WAN disconnect/reconnect

    • DHCP renew

    • session reset

  3. Run a continuous ping before and during the event
    For example:

    ping 8.8.8.8

    This helps confirm whether the WAN link itself drops.

  4. Also check OpenWrt logs just in case

    logread | grep -i wan

    around that timestamp, to see if it’s simply reacting to a WAN drop.

Since the timing is so precise and persists across reboots, it’s very unlikely to be random or device-specific. Something external is triggering it on a schedule.

Let us know what you find from the Zyxel side — that will likely give the final answer.