Sorry if there is already a thread on this, but I have not managed to find an answer to this question on either google or this forum. Everything I bump into only describes what a bridge interface is, but none of them explain the purpose of it in openwrt.
I just switched the firmware on my router to openwrt, and noticed the extra interface br-lan containing eth0. My natural reaction was to remove it, but since I'm new to openwrt I thought to figure out first what it's there for. I used to think I knew a thing or two about networking, but this, I can't figure out for the life of me.
Why is there, on a fresh install, a bridge interface that seemingly consists of only eth0? What I am missing or not seeing or lacking in knowledge?
A bridge interface is like a virtual Ethernet switch. It lets you connect more than one thing to the "port" (interface) in the kernel that holds an IP address. The usual usage is to connect both Ethernet and wifi to the lan network*. On a dual band router there may be two APs connected, one for each band. On a wired only router the br-lan is still set up for the possibility to add something later. There is a really insignificant performance drop going through a bridge with only two ports (the kernel and the eth port) compared to a direct connection, it doesn't hurt to leave it in.
wifi interfaces connected to a bridge are specified in the wireless configuration they won't appear in the network configuration.
I had a suspicion it might have something to do with that, but your answer in particular also made me curious as to why it is setup that way so it got me googling, and bumping into this thread from a couple of years ago:
So it seems there already was another similar post on this matter that I obviously missed (funny enough, you also helped in answering that one too =).
Just thought to mention it in case someone bumps into one first, and wants a little more info on the matter.