I believe this question has been answered a 100 times before, but I'm almost sure that I'm searching into the wrong direction. My desired setup is the following:
I have a virtual host using KVM and libvirt. I have a simple 192.168.1.0/24 home network, which I would like to extend by a server network. I will use 192.168.12.0/24 for the new network. But since there will be a few servers still running in the normal network, I added a virtual network to libvirt. Basicly I would like to route between br0(which is a bridge to eth0) and virbr0(which is the virtual network interface).I have tried to route the traffic using iptables and I have managed it to gain access to the network using these commands
iptables -I FORWARD -d 192.168.12.0/24 -s 0.0.0.0/0 -j ACCEPT
iptables -I FORWARD -s 192.168.12.0/24 -d 0.0.0.0/0 -j ACCEPT
iptables -I FORWARD -s 192.168.1.0/24 -d 0.0.0.0/0 -j ACCEPT
iptables -I FORWARD -d 192.168.1.0/24 -s 0.0.0.0/0 -j ACCEPT
Could someone show me the right direction?
EDIT 1: Thanks for your answers. I completely forgot about the kernel rules and applied them. I am now able to ping the machine from the 192.168.1.0/24 network and vice versa. But I unfortunately am not able to connect via ssh to this machine neither is it possible to ping anything else then 192.168.1.0/24 (and its origin network of course). The "core" router is properly configured, to route anything to the server network, to the kvm hypervisor.
I also thought about the bridge as routed interface, and I added a new interface (eth0:1) which is now my "outside" interface, but this also doesn't change anything.