Bridging Virtual Interfaces breaks networking... entirely

Hey everyone,

I had something peculiar happen a while back when I tried to bridge two vlans together in an LXC container and later a VM. As far as I understand it, L2 bridging between vlans should be perfectly fine as long as there isn’t a router or competing broadcast service like DHCP that would cause issues. I did it with my vlan 40, which is my standard devices network, and vlan 310, which only exists on the switches and didn’t have anything else on it. When I bridged these two it seemed as though I caused a broadcast storm but that shouldn’t have been the case. (It may have been caused by the fact my router is virtualized on the same host that I did this on, but it still shouldn’t have had this effect.) The goal that I had with this was to create a “VWire”/L2 firewall so I can monitor and block traffic at layer 2 to be a transparent firewall to see if I could replicate the functionality of PaloAltos vwire. I’m not fully sure what happened and testing seems to crash the entire network so I’d like to get a handle on what’s actually happening. I’m posting here as well so see if anyone had linux bridging experience.

For some more information like configurations:

I figured out my issue. Spanning tree was the culprit in the end as it was shutting down the vlans on the port the VM Host was connected to. Fixed by setting spanning-tree bpdufiltering enable on the cisco switch port.

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