how the bridge interface behaves is well said in viewtopic.php?p=1004571#p902366
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- If the CPU-Port is set untagged, this is the only way to communicate with the Bridge Interface (itself) and services "behind", like DHCP, NTP... In this state "bridge1" is CPU-Port and Interface.
- If the CPU-Port is set tagged, you will need a dedicated VLAN-Interface - bound to the bridge. But you won't be able to connect to the Bridge Interface itself! Services behind are reached through this dedicated VLAN-Interface via the CPU-Port (called "bridge1", but this refers to the CPU-Port only - not to the Bridge as a dedicated Interface).
but where to use the Bridge Interface?
Can I use it somewhere else, e.g. Firewall, Queue, etc. to e.g. simplify things like instead listing all VLAN interfaces or their IP Ranges, I select the bridge which includes all underlying elements.