Question About Bridging Interfaces

Hello everyone, I have a (hopefully) simple beginner question.

when I was choosing a computer to install routing software, I constantly came across people who were trying to bridge their ports to act like a switch. Numerous posts said this is a bad idea, and to buy a switch (I believe I understand the reason).

When I installed OpenWRT, I attached a switch to one of the ports on the computer like everyone was saying. All my devices are attached to the switch.

However, when I look at the network interfaces section, I see the lan is bridged (br-lan), and the checkmark for "bridge these interfaces" is checked as well. I have a really basic setup out of the box.

Would someone be able to explain to me why its bridged? I thought it was very inefficient to do this. I know pfsense is different, but the explanation sounds like it applies to all routing software.

Thanks to anyone if they could help.

All the ports on the external switch are bridged together on the switch, so the traffic between nodes in your network does not reach the router. This is good, because you are not bridging the connections internally on the router.

The LAN interface has to be a bridge, because the wireless access points need to hook to a bridged interface.

In other words, there is nothing to worry about.

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When there is only one physical interface in a network (such as your x86 with one eth port and no wifi) you can uncheck the bridge box to have the kernel place an IP address on the port directly. The performance improvement is basically un-noticeable though.

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Hi thanks very much for the reply. I had to do some extra reading based on what you said. If you don't mind, can you clarify If I am right?

  • So since "bridge interfaces" is checked on the 'lan' interface physical settings, it does not necessarily mean that its currently bridged to another interface (you have to choose the interfaces, which is just below the options. In my case, interface eth0 is the only one selected, which means nothing is bridged yet).

  • So 'lan' has bridge enabled by default to connect other interfaces to it (such as Wireless APs). What I actually have right now is my wireless access point attached to on of the ports on my only external switch, and that switch is attached to x86 router as eth0 lan interface. Are you by chance saying its better to attach wireless access point using one of the other interface ports on my x86 router (there's six) and the bridge that to the eth0 lan interface? Or am I over thinking this? Right now everything works on my home network.

Your LAN interface is a bridge so you can attach an internal access.point to it. External access points do not need that bridge.

If you attach the AP to the router, traffic between wired and wireless clients will travel through the router. This has advantages and disadvantages.

No you have a bridge with only one active hardware port (and the inherent kernel port) which is like an Etherenet switch with only two cables plugged in. It's unnecessary since you could run a cable directly instead. On the other hand having the switch already there makes it simple to expand the network. A kernel network bridge is very much a software emulation of an unmanaged switch.

The brctl show command will show the bridges and their members.

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Hi thanks alot for you replies. I believe I'm beginning to understand. This is a good start to help me out, and I will try the command you suggested to get a better understanding. I thought that in the physical settings, I would see "eth0" and "kernel?(or something like that)" but I didn't see that, so it lead me to believe nothing was bridged to the default lan interface, even though the "bridge interface" box was checked. But its clear from your reply I have more reading to do, as this is probably basic knowledge I should know.

Thanks for your help! Much Appreciated!

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