WAN freezes with no log entries — only reboot fixes (Zyxel EX5601-T0, OpenWrt 24.10.2)

Installing and Using OpenWrt
1

Hi everyone,
I’m experiencing a strange WAN connectivity issue on my Zyxel EX5601-T0 running OpenWrt 24.10.2 r28739-d9340319c6 / LuCI openwrt-24.10 branch 25.168.50434~d6b13f6.
Around 01:00 AM on December 11, my Internet connection stopped working completely — but the router itself remained accessible on LAN and Wi-Fi, and there were no log entries indicating WAN down/up, DHCP renewal, PPP events, or link issues.
At 02:00 AM, I rebooted the router manually, and everything immediately came back online.

  • No WAN-related errors in logread or dmesg between 01:00 and 02:00
  • The Ethernet WAN port did not flap (no link down/up events)
  • Only a full router reboot restores connectivity
  • IPv4 and IPv6 stop passing traffic when the issue occurs
  • DNS also becomes unreachable
  • The system time could not be synced (external NTP unreachable)

My upstream modem/router (a FritzBox) logged multiple errors during the outage:

The time server 2a00:17c0:c6::1:2 is not responding
The time server 2a00:1288:110:f600::1001 is not responding
The time server 2a00:f8c0:8000::224 is not responding

This confirms that the WAN connection from the OpenWrt router was actually down, even though the interface appeared to be up.

What I already checked:

  • logread → no WAN events
  • dmesg → no kernel messages related to MT7531 / Ethernet / netifd
  • ifstatus wan → shows normal state even during the outage
  • Router load, memory, temperature → normal
  • No firewall reloads or network restarts around the time of the failure

Device info:

Router:** Zyxel EX5601-T0 (ISP-branded version, WindTre Italy)
OpenWrt:** 24.10.2 r28739-d9340319c6 / LuCI openwrt-24.10 branch 25.168.50434~d6b13f6
WAN:** DHCP (not PPPoE)
Hardware:** MediaTek MT7986A + MT7531 switch

  1. Is this a known issue with MT7531 or netifd not logging link freeze events?
  2. Is there any recommended debug mode to increase WAN/switch logging?
  3. Would enabling logd persistence help?
  4. Should I test disabling IPv6 delegation to rule out prefix-renewal bugs?
  5. Is a WAN watchdog script commonly recommended for this type of silent freeze?

I’d appreciate any suggestions, patches, or debug steps I can run to diagnose this properly.
This issue is quite problematic because it leaves no trace in the logs and requires a manual reboot.

Thanks in advance!

2

Do you still have ip4 connectivity?

Please connect to your OpenWrt device using ssh and copy the output of the following commands and post it here using the "Preformatted text </> " button (red circle; this works best in the 'Markdown' composer view in the blue oval):

Screenshot 2025-10-20 at 8.14.14 PM

Remember to redact passwords, VPN keys, MAC addresses and any public IP addresses you may have:

ubus call system board
cat /etc/config/network
cat /etc/config/wireless
cat /etc/config/dhcp
cat /etc/config/firewall
3

I use a T-56 as lab rat, so no heavy load, but no issues, ever.

Tried pulling the wan cable while it appeared to be down ?

Have you by any chance applied the 2.5gbit WAN and LAN ports ethtool workaround to avoid flapping at 1gbit ?

I'd however start by upgrading to 24.10.4.