B5-Lite Trunking Bug

I’ve inherited a couple of B5-Lite radios for backhaul for a given site that I must now support. We installed a new larger network cabinet, with a new UPS, and trying to bring up this site after this physical work led to an interesting problem. On the either side of the B5-Lite radios, we have a couple of Cisco Catalyst 3560 switches that connect to the rest of the in-building networks, but very strangely, if the B5-Lite radios boot up while being connected to the Cisco Catalyst 3560 switches, I can not ping any IP addresses or transmit any layer 3 traffic across the PTP link, even though the link is up, and I can learn MAC addresses across either side on multiple VLANs, and ARP is resolving IP addresses. I was very perplexed by this, and spent nearly 2 hours troubleshooting scratching my head thinking “EVERYTHING LOOKS RIGHT! WHY DOESN’T IT WORK ANYMORE!?!?!”

Lo and behold, and I look up firmware release notes at http://backhaul.help.mimosa.co/backhaul-firmware-release-notes-b5-lite and find this under Known Issues:

Known Issues

• If both the backhaul radios are attached to Cisco 3550 or 3750 switches and the Dynamic Trunking Protocol on the switches is turned on, connectivity to the device’s management IP may fail. The workaround is to turn off the Dynamic Trunking Protocol on the trunk port.

Which was exactly my problem, because I have to trunk multiple VLANs through this PTP link. Except it wasn’t just the management IP that was unreachable, it was all ICMP/TCP/UDP traffic, for both management and the site’s data VLAN. Setting both trunk ports to “nonegotiate” does not fix the problem. My only work-around is to physically go to the buildings, disconnect the radios from the switches, let the radios reboot and finish booting all the way, and then re-connect the Cisco switches. And then it will work fine from then on, as long as the radio doesn’t reboot while the Cisco switches are still connected and online.

Looking through the Firmware Release Notes history, this problem has existed at least since version 1.5.0, released 2018-04-17 (when these radios went in), and it still exists as of version 1.5.4 (latest available), released 2020-10-09. I confirmed that the problem is still present in version 1.5.4 by upgrading both radios and reproducing the problem using the same steps.

This is an extremely problematic bug for us. Is there any chance Mimosa will ever issue a patch for this bug?