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I have just learned about bridged mode networking in VMWare and I wonder how is it different from the "bridge" used in physical world networking? According to what I've found myself so far, I guess they are two completely different things.

A network bridge is a layer 2 device that uses the MAC addresses of devices on the network for allowing them to communicate with each other, without the need for defining networks and assigning ip addresses. While the bridged mode networking in hypervisors like VMWare, uses ip addresses and lets the virtual guests stand out as independent nodes on the network as if they are separate physical devices. So I think there's not much similarity between these two, however, I'm still learning and would be happy to know if I'm wrong. The similarity in their namings made me hesitate so I'm asking. Thanks in advance.

  • "A network bridge is a layer 2 device that uses the MAC addresses of devices on the network for allowing them to communicate with each other," That is true only for data-link protocols that use MAC addresses, but not all do. The IEEE LAN protocols use MAC addresses (some use 48-bit MAC addresses, and some use 64-bit MAC addresses). Other data-link protocols use different addressing, or no addressing at all. – Ron Maupin Aug 23 '19 at 13:13
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    VMware ESXi or Workstation? There are fundamental differences and I don't think Workstation is on-topic here at all. – Zac67 Aug 23 '19 at 15:14
  • Did any answer help you? If so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you can provide and accept your own answer. – Ron Maupin Dec 15 '19 at 18:37
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Bridge mode

is the configuration that disables the NAT feature on the modem and allows a router to function as a DHCP server without an IP Address conflict. Connecting multiple routers can extend the Wi-Fi coverage in your office/home. ... Bridge mode fixes this by letting multiple routers share one single Wi-Fi network.

Network Bridge

A network bridge is a computer networking device that creates a single aggregate network from multiple communication networks or network segments. This function is called network bridging.[1] Bridging is distinct from routing. Routing allows multiple networks to communicate independently and yet remain separate, whereas bridging connects two separate networks as if they were a single network. In the OSI model, bridging is performed in the data link layer (layer 2). If one or more segments of the bridged network are wireless, the device is known as a wireless bridge.

I think this explanation will help to understand what Bridge mode and bridging in networking. Clearly Bridging is Not routing and Router can configure in Bridge mode as well.

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I must stress that VMware (ESX) vSwitch and dvSwitch are not true bridges. They do not track MAC:port based on traffic. They do build a "CAM" table, but it's based on VM static configuration, not dynamic actual traffic. This becomes a huge problem when attempting to "nest" VMs (i.e. run ESX as a VM) -- the host vSwitch will not know anything about the layer-2 addresses of any VMs it is not natively running.

(There's a fling to add proper bridge learning to dvs, but it's more of a mess than a solution.)

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  • You're making a good point - however, bridges are not necessarily self-learning even though all practical "real" bridges are. – Zac67 Aug 23 '19 at 20:41

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