There are certain configuration that are known to have major flaws by design and should be avoided by all means possible. Misconfigured Layer2 can sometimes cause hard to detect network errors, random performance drops, certain segments of a network to be unreachable, certain networking services to be malfunctioning or a complete network failure. This page will contain some common and not so very common configurations that will cause issues in your network.
VLAN on a bridge in a bridge
Consider the following scenario, you have a set of interfaces (don't have to be physical interfaces) and you want all of them to be in the same Layer2 segment, the solution is to add them to a single bridge, but you require that traffic from one port tags all traffic into a certain VLAN. This can be done by creating a VLAN interface on top of the bridge interface and by creating a separate bridge that contains this newly created VLAN interface and the interface, which will send out tagged traffic. Network diagram can be found below:
/interface bridge add name=bridge1 add name=bridge2 /interface vlan add interface=bridge1 name=VLAN vlan-id=99 /interface bridge port add bridge=bridge1 interface=ether1 add bridge=bridge1 interface=ether2 add bridge=bridge2 interface=VLAN add bridge=bridge2 interface=ether3