Hi,

I have several VMs on KVM with virtual machine manager that I don't want to use NAT with, I want them to get a IP from the same source as the host machine, from the external DHCP. For this purpose, I want to do level 2 bridging, so the virsh networking "switch" or interface is directly bridged with the physical NIC of the host OS. This has so far not worked, when setting up the bridge, it keeps asking me for an IP and range, but Level 2 bridging has no IP, level 2 is below IP and just lets all traffic through.
I think that people today confuse what a bridge is and lump together other technologies to join virtual NICs.

I have noticed that this is super simple when you use Microsoft HyperV or VirtualBox, but pretty difficult with KVM and virtual machine manager. There is hardly any documentation and nobody seems to use KVM much at all.

Right now, when I use KVM to run my VMs, they get a IP from the internal virsh DHCP and are not reachable from external machines, which is a problem.

I agree that VMM is somewhat less comfortable than VirtualBox, but what you say does not make much sense to me.

What keeps you asking? How exactly did you set up the virtual network?
If they are bridged, they are connected to the same network as the other devices. Except if the VM host blocks or otherwise manipulates traffic. It seems your VMs are not bridged.

To help you, I'd like to see the output of
where VM is one of those VMs that you have trouble with.

When I read the instructions on how to setup bridges via different means, it often has instructions to set an IP for the bridge, which does not make sense to me.
That is how the questions start, I use virt-manager on Debian 10 and I'm confused on how I can get a level 2 bridged NIC in my VM that is directly connected to the host interface.
I have to admit that I don't have much experience setting up virtual networks on KVM via virsh, virt-manager doesn't offer many possibilities.
I keep coming across macvtap, which seems to offer bridge functionality. That seems to use a more direct connection via the virtual NIC for just one VM, while there is another possibility to define a whole virtual network.

Yeah, I don't think it is bridged right now.
I'm honestly pretty confused on how to setup a virtual network on KMV / QEMU, it is likely not VM specific, but applys to the whole virtual network.
I basically just want that VM to get attached to my host NIC like it was physically connected to the VM and when it sends out DHCP requests, it will get an IP the same way that the host gets one.
I actually want to use KVM and avoid virtualbox as it is the built in solution on Linux. And the VMs also work pretty well, except I have always struggled with the networking. Normally, the VMs seem to be connected to use NAT to get out to the external net, but I need these VMs to be accessible from outside (which NAT normally blocks)

Create a bridge on the host then point at that.

Without knowing what you did to set up the network, nobody can help you. Try providing information instead of repeatedly stating that you are confused.

I did not set up any network. I used the default network that was already established. That is for NAT, which does not work for my use case, it sets up a local network on the VM host that is 192.168.122.0/24, including a local DHCP for it. 192.168.122.1/24 is not accessible from outside of this VM host (192.168.1.220)

I have quite a bit of experience in TCP/IP networking, but bridging is something I have never been able to get working.
I basically don't know how you setup networking with virsh, what the options are etc. My goal is to get several guest VMs to use the DHCP server on router 192.168.1.1 (serving network 192.168.1.1/24) to get an IP that is on the same network as the VM host (192.168.1.220). I'm trying to use bridging for that, I don't know if that is the recommended way, but I don't see how DHCP discovery requests from the guest VMs could otherwise arrive at 192.168.1.1 and then have a DHCPOFFER traverse back to the guest VM. The guest VMs will all be on several different physical VM Hosts (all on network 192.168.1.1/24) that all need to get IPs in network 192.168.1.1/24

When I take a physical laptop and plug it via ethernet, it will get an IP on network 192.168.1.1/24, I need all the guest VMs to get IPs on the exact same network via the same DHCP.

This hope I have expressed myself clearly, on the risk of having included redundant and obvious details.

https://wiki.debian.org/BridgeNetworkConnections

Do that. Your mistake is you are trying to use virsh to run the networking. You need to bypass it. Point the VM at br0 (or whatever you call it) in virt-manager. When this is done the VMs are just another machine on the lan.

Yes, that worked. I just created the bridge outside virsh, on Linux, added the ethernet interface to it, set that to promisc and set the IP on the bridge interface (I was confused on how the bridge works on the different OSI layers), then adding the virtual machine to that bridge does the trick. The default gateway still has to be changed.