[BUG] CORE One L 6.5.3-RC - Wi-Fi connected, DHCP lease present, but printer unreachable on LAN until reboot

[Taxom]

Printer model

CORE One L

Firmware version

6.5.3-RC

Upgrades and modifications

No response

Printing from...

PrusaLink / Local network

Describe the bug

The printer connects to Wi-Fi successfully and shows as connected in the Network Status menu.
The printer reports:

• Wi-Fi Status: Connected
• IPv4 Address: 192.168.1.131
• Gateway: 192.168.1.1
• MAC: 8C:4F:00:E6::

My router also shows an active DHCP lease for the printer with the same IP and MAC address.
However, when this happens:

• the printer does not respond to ping
• the PrusaLink web page does not open
• the printer is effectively unreachable on the local network

From Windows, ping returns:
Reply from <myPC IP>: Destination host unreachable.

The problem is fixed by rebooting the printer, but sometimes it takes more than one reboot before the printer becomes reachable again.

So the printer appears to stay associated with Wi-Fi and keep its DHCP lease, but the network stack or interface stops responding on the LAN side.

How to reproduce

This is intermittent, but the pattern is:

1. Turn on the printer
2. Let it connect to Wi-Fi
3. Confirm that the printer shows "Connected" in Network Status
4. Confirm that the router shows an active DHCP lease for the printer
5. Try to ping the printer or open PrusaLink
6. Sometimes the printer is unreachable even though it appears connected
7. Rebooting the printer restores connectivity

Environment:

• Isolated local Wi-Fi network
• router sees the printer associated on WLAN
• DHCP lease is present and matches the IP shown on the printer
• issue started / observed on firmware 6.5.3-RC

This does not look like a DHCP assignment failure, because the printer gets an address correctly and the router keeps seeing it. It looks more like the printer becomes unreachable on the network stack side while still appearing connected.

Expected behavior

No response

Files

No response

[bkerler]

Could be that the wifi module got broken, try to reflash it. Other than that, I don't think it's a fw bug but more network related. We do know of some bugs related to wifi + network with large udp payloads (broadcast), WPA2/WPA3 transition and also for cases with APs being repeated (same SSID, but different signal strength) for which fixes are currently being prepared.
If you want to be sure what's causing this issue, sniff your network and see what happens with the packets.

Make sure that you haven't got multiple devices allocated with the same IP or name, as this might cause a network conflict, same for possible MDNS, tagging, firewall or broadcast issues. Could be gateway related as well.

[Taxom]

I have one single AP, the printer's IP is allocated in Static Leases. At the same time, the printer manages to make a DNS request to buddy-a.connect.prusa3d.com and prusa3d.pool.ntp.org, to the first it of course does not receive a response, since the network is isolated, to the second it receives the local NTP address.
WiFi settings WPA2 AES channel 6 20/40.

After restarting, if the printer does not try to access buddy-a.connect.prusa3d.com, it becomes accessible over the network, I believe that the reason is that it cannot access this address and freezes.

Could you provide a link to flash the WiFi module? Although I don't think that's the problem.

[bkerler]

The esp module is automatically flashed when upgrading the bootloader or if the version does mismatch. Also it does verify the module content on every reboot, so I doubt this is the problem (just reviewed that part). Yeah, I assume the problem might be that the needed connect url isn't reachable due to your network setup.

[Taxom]

Yeah, I assume the problem might be that the needed connect url isn't reachable due to your network setup.

Then this is really a bug that needs to be fixed, otherwise the meaning of PrusaLink, whose purpose is access over a local network instead of PrusaConnect, is lost.

[bkerler]

If it were a bug in the firmware, many users would experience it :) I know, this isn't helpful, just stating that at least for me, I'm not having such an issue and I use prusalink regularly. As said, I'm very sure that there is some kind of network issue in your setup (such as route or gateway setup) and you likely will need to sniff the packets to see what's going on.

[Taxom]

I don't think many people use the printer on an isolated network; most users use PrusaConect. As I already wrote, the printer stops responding after trying to connect to buddy-a.connect.prusa3d.com, this should not happen.

[bkerler]

If you state LAN, you do you mean Ethernet connection ? Or that you are connected via Wifi to the local network (Ethernet disconnected) ?

[Taxom]

If you state LAN, you do you mean Ethernet connection ? Or that you are connected via Wifi to the local network (Ethernet disconnected) ?

Yes, this is a dedicated local network without Internet access, for IoT devices. Its settings are simplified as much as possible for devices connected to it (especially those based on ESP). For security and privacy reasons, this network does not have access to the Internet; the network has its own NTP server for devices.

One of the most important requirements for purchasing Prusa was the ability to work autonomously without access to the Internet, and the emerging problem calls into question this possibility.

[bkerler]

I think I spotted the issue, not related to the url in fact but to the fact that if a connection has no inbound traffic, the esp would disconnect and thus dhcp lease affected as well. I wrote a PR #5188 to fix that issue .. if a connection is associated and the link is up but no inbound traffic happens (thus idle), it is now not reconnected. Sorry for not seeing the issue earlier as I thought you meant Ethernet with LAN :)

[Taxom]

I think I spotted the issue, not related to the url in fact but to the fact that if a connection has no inbound traffic, the esp would disconnect and thus dhcp lease affected as well. I wrote a PR #5188 to fix that issue .. if a connection is associated and the link is up but no inbound traffic happens (thus idle), it is now not reconnected. Sorry for not seeing the issue earlier as I thought you meant Ethernet with LAN :)

In general, this is strange, since my Home Assistant should keep the connection with the printer active, but perhaps this is not enough to prevent the ESP from turning off.

[bkerler]

If you want I can create a custom firmware so you can test my PR, but you'd need to break the appendix on the board to flash custom firmware.

[Taxom]

If you want I can create a custom firmware so you can test my PR, but you'd need to break the appendix on the board to flash custom firmware.

No, I’m not ready to lose the warranty yet; the return period hasn’t even passed yet))

[bkerler]

You won't loose the warranty by breaking the appendix, see : https://help.prusa3d.com/article/flashing-custom-firmware-mini-mini_14