PPPoE established - connectivity to router lost


I've recently bought a MikroTik hEX S (RB750Gr3) and flashed it with OpenWRT (19.07.7). Everything runs fine, except for the PPPoE connection to my ISP. Once that establishes, I loose ALL connectivity to the RB. Ethernet LEDs keep blinking, so there must be some logic still running, hoewever, there's no serial console to verify. I can change the PPPoEclient to a DHCPv4 client on the same interface and zone and let the ISP's router handle the PPPoE stuff. That works well, but I would like to avoid the hardware from my ISP if possible.

I've tried recreating the PPPoE interface, enabling/disabling IPv6 and enabling/disabling automatic gateway. Ideally, I'd be able to access the logs in some way to figure out what is goig on, but I can't reach the RB anymore until I reboot. And than (most) logs are gone. So I'm finding myself at a dead end at the moment. Anyone have any idea where to go from here?

edit: for what it's worth, the same setup with a vanilla ER-X works great. Well... not great, but it sets up a PPPoE session without stopping all other traffic at least. So that should exclude foul play from my ISP.

Thanks in advance!

Are you using Luci or are you applying the configuration changes from an SSH connection?
Are you connected on the lan ports of this router or from the internet?
Are you using the internet port as PoE input or are you using the DC jack?
Is it possible to show us the configuration changes you are applying after a clean install? (either in Luci or in console)

Two ideas:

  1. Leave an SSH terminal running logread -f while you start the PPP connection. You might see a command that is taking down the LAN interfaces, not setting firewall correctly, etc.

  2. You mention a serial console. Can you add one?

logread -f looks to have been a great idea! I'm losing connectivity right after "user.notice firewall: Reloading firewall due to ifup of pppoe". Oddly enough, the firewall rules are applied to the zone WAN (not an interface). So not sure why DHCPv4 works and PPPoE doesn't. But at least there's something to look at now!

There are solder pads on the board that are big enough in se, but they're very close to some other, very tiny components. I'll try looking at the firewall settings first :slight_smile:


You could try unplugging the WAN side cable to see if ifdown on the WAN brings LAN connectivity back. Then a cron job to put the firewall rules into a log every minute so you can compare what is there when WAN is up and down.

You could also try /etc/init.d/firewall reload without doing anything with WAN to see if it causes the same problem.

Have you changed anything from stock? Ports, switch assignments, firewall.user rules, additional software packages, etc?

Well.. the RouterBoard does not respond at all anymore now. Not after a reset, not after TFTP boot,... I think it is ready for the parts pile. This thing has taken a lot more time than I would have liked anyway.

Nevertheless, thank you for thinking along.