destination MAC) and doesn't even look at the higher layers such as IP. (This is often called the 'CPU port'.)Ī bridge is very different from a router it doesn't need any IP addresses to function: it works at 'layer 2' or the 'MAC layer', which means it forwards packets purely based on their Ethernet header (e.g. Similarly, if you have a managed 8-port Ethernet switch, it really has 9 ports: one of them connects internally to the management CPU, which allows that switch to be configured through the network.

(You could imagine that the actual 'bridge' exists somewhere behind br0.)

and a bridge port that allows the host OS to be a member of the same bridge.įor example, when you configure a bridge br0 with two ports eth0 and eth1, in reality it has three: the third one is br0 itself.

the actual layer-2 bridge, which connects all of its assigned 'ports' without any IP processing.

The first thing to understand is that the Linux 'br0' interface represents two objects at once: One of which is the regular network connection, the other is associated with the bridge. If a bridge connects two networks together as if they were the same network, why does it only have one associated ip address? (How does a bridge actually work? I wasn't easily able to find any helpful information about this online.)īy the way, here's a screenshot of the virtualization host ip a output: As you can see there are multiple NICs on my VM host. Why does it work when the bridge has a 'random' ip address, such as 192.168.10.1? I don't have a 192.168.10.X network here, I made that number up.

Why did creating a bridge with an IP address on the same network as the 192.168.1.X network break network connectivity? Here's where my confusion start and the questions arrive. I then booted up a VM with this network configuration:Īnd it is able to connect, and obtains the IP 192.168.1.190 from my DHCP server. This seemed to work and I was able to create a new virtual network which uses the bridge. When I tried again to configure my system, I chose to give the bridge a static ip of 192.168.10.1/24. I know it is used to join two different networks together as if they were the same network. My main issue extends from the fact that I don't have a clear picture as to what a bridge actually is or represents. This took down my network connection to the VM host, which itself is on that network. I tried following this, creating a bridge myself one the network 192.168.1.X/24. However no explanation as to why this was the case was given.

I have read a series of other guides available online, however they all seem to skip over the details of the IP configuration and don't give any details as to why particular addresses/networks and gateways have been chosen.įor example, in the linked example above, a bridge is created with the address 192.168.0.90, on the network 192.168.0.X/24. I have followed a few guides to getting a bridge setup on my Debian VM host

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