[BUG / FIRMWARE REQUEST] Nebula FWA70 – LAN Client loses IP/Connectivity after Carrier 24h Reconnect

aluhuetchen

Dear Zyxel Team and Community,
I am writing this post to report a reproducible and critical firmware bug on the Nebula FWA70 regarding connection recovery after daily provider reconnects / cell state changes, and to request a permanent fix in upcoming firmware releases.

1. The Issue & Symptoms

In Germany, Deutsche Telekom enforces a daily reconnect / IP renew cycle (or transitions cell towers into night/power-saving states).
Whenever this carrier-side reconnection happens:

• The FWA70 fails to properly re-delegate/renew the IP address (especially IPv6 / DHCPv6 lease and routing) to connected LAN clients / downstream routers.
  
• The downstream client/router completely loses internet connectivity and cannot obtain a valid IP/lease from the FWA70.
  
• The connection remains dead indefinitely until either the FWA70 is fully rebooted or the WAN interface is manually toggled via CLI.
  

A simple DHCP renew initiated from the downstream client does not solve the problem. The FWA70's internal bridging/DHCP/routing daemon appears to get stuck in an invalid state after the cellular reconnection occurs.

2. Root Cause Analysis & Confirmation

To diagnose the problem, I set up SSH access to the FWA70 from my downstream OpenWrt router.
I discovered that a full physical reboot is not strictly necessary—the connection recovers immediately as soon as the cellular interface is bounced via the ZySH CLI:

zycli wan active servicename "Cellular WAN 1" --Status disable
zycli wan active servicename "Cellular WAN 1" --Status enable

Once these commands are executed, the 5G connection re-establishes, the FWA70 properly re-assigns the IP/gateway to the LAN client, and traffic flows immediately.
This proves that:

1. The cellular hardware itself is fully operational.
   
2. The issue is a firmware-level state handling bug inside the FWA70, where the internal networking stack fails to restart its LAN-facing DHCP/routing daemons when the WAN connection drops and reconnects automatically.
   

3. My Current (Temporary) Workaround

To keep my network usable 24/7 without manual intervention, I had to develop an automated watchdog script running on my downstream router via Cron:

1. The script pings public DNS servers (IPv6 / IPv4) every few minutes.
   
2. If connectivity fails, it attempts a local interface renew.
   
3. printf 'zycli wan active servicename "Cellular WAN 1" --Status disable\nexit\n' | sshpass -p "PASSWORD" ssh -T -y admin@192.168.1.1
4. sleep 3
5. printf 'zycli wan active servicename "Cellular WAN 1" --Status enable\nexit\n' | sshpass -p "PASSWORD" ssh -T -y admin@192.168.1.1
6. If that still does not recover the link, it triggers zycli reboot as a last resort.
   

4. Conclusion & Request to Zyxel R&D

While this workaround keeps my connection alive, it should not be required on a premium-priced, enterprise/prosumer-grade Fixed Wireless Access device like the Nebula FWA70.
Users should not need to run custom SSH scripts and cronjobs just to survive a standard carrier reconnect.
Feature Request / Bug Fix:

• Please ensure that when the cellular connection drops or re-establishes, the FWA70 internal daemons automatically trigger a clean interface re-initialization and send appropriate Router Advertisements (RA) / DHCP renewals to downstream LAN devices.
  
• Ensure that scheduled reboots configured via Nebula or CLI are reliably executed across all firmware versions.
  

I am happy to provide diagnostic logs, syslogs, or further technical details if the development team wants to look into this.
Thank you

Zyxel_Tina

Hi @aluhuetchen,

Welcome to the Zyxel Community!

To help us investigate this issue further, could you please confirm the following details?

• When the ISP performs its daily reconnection, do you mean the router connected to the FWA70’s LAN port and all other clients using this network lose Internet access, while the FWA70 itself remains connected to the Internet?
  • Furthermore, these devices being unable to obtain a valid IP from the FWA70 and continuing to use their previous IP information?
• Do you mean restarting the cellular interface or rebooting the FWA70 restore Internet access for the downstream router and other clients?
• Is IPv4 affected as well, or is the issue only related to IPv6?
• Is the FWA70 managed through Nebula? If so, please enable Zyxel Support Access and provide the org/site names.

Additionally, please send the following information to us via private message:

• What are the model and MAC of the downstream router and the affected clients?
• A backup configuration file from the FWA70.
• The system logs captured while the issue is occurring. (Please note that the logs will be cleared if you reboot or restart the device before exporting them.)
• The approximate timestamp when the issue occurred.

Thank you for your cooperation.

aluhuetchen

Hi Tina,

Thank you for looking into this. Here are the answers to your questions and detailed information about my setup:

1. Downstream Router State & Behavior

When the ISP performs its reconnection, the downstream router loses internet access completely.

• Crucial detail: Even performing a complete reboot of the downstream router does NOT resolve the issue—it still fails to receive a valid IP/lease from the FWA70.
• The downstream device remains offline and without a valid IP until action is performed directly on the FWA70.

2. Recovery via FWA70 Interface Reset / Reboot

Yes, exactly.

• Restarting the cellular interface via ZySH CLI (zycli wan active servicename "Cellular WAN 1" --Status disable followed by enable) or performing a full reboot of the FWA70 immediately restores connectivity.
• Right after the FWA70 interface bounces, the downstream router successfully acquires its IP address and internet access is restored within seconds.

3. IPv4 vs. IPv6 & Network Details

My setup runs primarily on IPv6 (Deutsche Telekom 5G SA):

• In this mobile tariff, Telekom does not provide prefix delegation (no /56 or /64 PD).
• The downstream OpenWrt router receives a single IPv6 address on its WAN interface from the FWA70 and distributes IPv6 to internal clients using NAT66.
• When the carrier disconnects/reconnects, the FWA70 stops properly advertising or serving the IP on its LAN port, completely breaking this chain until the FWA70's WAN interface is restarted.

4. Management Mode (Nebula)

• The FWA70 is NOT managed via Nebula.
• It is operated purely in On-Premise / Standalone mode, managed exclusively through the local Web GUI and SSH.

Current Status & Requested Private Data

Thanks to an automated cron script on my downstream OpenWrt router, I have currently shifted the daily reconnect to 04:00 AM, which triggers the SSH interface bounce automatically and prevents interruptions during productive hours.