On the physical host, create a bridge br2
with eth2
in it, and another bridge br3
with eth3
in it.
Now any guest NIC you place in br2
will have access to whatever's on the other end of eth2
. Likewise any guest NIC bridged into br3
will have access to whatever's on the other end of br3
.
Just like you can have the physical system with eth2
and eth3
, you can have a guest with one interface in br2
and one interface in br3
. You can also just have a guest with one interface in one bridge only.
You can put a host IP address on the new bridges if you want to. If the host has no need to see what's happening on these other networks, then the host doesn't need to have an IP on these bridges. The Linux bridge is a software implementation of a network switch, so everything works at Layer 2, there's no routing involved which would require the host to have an IP address on the bridge.
You can call the bridges whatever you want (br2
,kitten1
,i_like_bacon
, etc) but I'd suggest something that makes it easy to identify either what the bridge is connected to, or what it's for. I try to follow the numbering of the underlying NIC, or an intrinsic name like office_lan
or dmz
.
I'd suggest not to have the names swapped around like eth2
in br3
and vice versa. One day you're almost sure to put an interface in the wrong bridge then spend a while wondering why it's not working.