The way I understand it is that a bridge domain is basically a set of ports that share the same flooding and learning capabilities. If you configure multiple VLANs (so not VLAN all) for a bridge domain, a separate bridge and learning domain is actually created per VLAN. JunOS uses this as a shortcut to create multiple bridge & learning domains.
See AlsoIP configurationManual:Interface/Bridge - MikroTik WikiVLAN - RouterOS - MikroTik DocumentationCommunication between different VLANIf you create a bridge domain with VLAN all (1-4094) and traffic enters via a logical interface on VLAN 100, it is bridged to all interfaces in the bridge domain, where the ingress port could discard it if it does not have a logical interface for VLAN 100. Not a very effective way to bridge traffic.
I have to admit… I am incredibly confused here… I also read through Chapter 2 of the MX-960 book by Reynolds, and I am even more confused...
I also couldn't find any further details on the Juniper website (unless I'm looking in the wrong places).
I still don't get the difference between a Bridge Domain and VLAN. Above says:
a bridge domain is basically a set of ports that share the same flooding and learning capabilities
How is this different than a VLAN?
I come from a Cisco background, so I'm trying to relate the concepts of Bridge Domain and VLAN to everything I've learned from Cisco/Cisco Press.
Let me give you an example. On Cisco Catalyst switches, we can consider a VLAN a single broadcast domain. In the Reynolds book, he defines a Bridge Domain as:
A bridge domain is simply a set of IFLs that share the same flooding, filtering, and forwarding characteristics. A bridge domain and broadcast domain are synonymous in definition and can be used interchangeably with each other.
He even says that a bridge domain is synonymous with a broadcast domain.
So according to Cisco, a VLAN is a Broadcast Domain.
According to Reynolds, a Broadcast Domain is synonymous with a Bridge Domain.
Therefore VLAN = Bridge Domain
Except, that's not the case...
Is there an equivalent concept to a Bridge Domain in the Cisco world? I'm familiar with taking a bunch of interfaces, putting them all in a VLAN, and that's it. We can create a VLAN, add ports to it, define the VLAN on trunks, and there isn't much else.
Don't even get me started on the concept of a Learning Domain.
Reynolds say that:
Bridge domains require a method to learn MAC addresses. This is done via a learning domain. A learning domain is simply a MAC forwarding database.What does he mean that bridge domains require a method to learn MAC addresses. Isn't the method known as backward learning? A node forwards a frame into the network and the switch records the MAC Address.
Any assistance would be appreciated. Any additional reading materials would also help. Can't seem to find much else. I thought the Reynolds book would set it all straight, but it's left me with more questions than anything else. Yes, I've gone through the chapter a few times.
