I am following this guide on installing my first KVM HV.

The thing I do not understand is the bit about bridge network setup. It states it is optional, but what are the benefits, should I be doing this? Can I just set public IP's on the VM's themselves and make networking work that way? I only have 1 network adapter, my host has a public IP of 81.xx.xx.xx and my VM's will use the same segment of addresses.

  • IIRC, You don't have to setup a bridge interface to be able to bridge your VM NIC to the physical NIC. But it try it and you fail you sould create one. – Rabin Sep 23 '14 at 10:58
  • @Rabin So I can just set the IP addresses on the VM and it should work. Sorry, this is my first time getting involved and I am trying to learn, so pls excuse my 'noobishness' – W Khan Sep 23 '14 at 11:03

when you set a bridge, it acts as a virtual switch for the VMs to plug into. The bridge IP will be used for the host, and the VMs plugged into the bridge, with IPs from the same subnet, will be on the same L2 domain.

The other options are:

  • NAT: In this case, the VM is running inside a virtual network inside the host, isolated from the public network the host is on. You can play with iptables rules to open ports to the VM, but the host is acting as a router for the VMs
  • macvtap, pci passthrough, SRIOV, 802.1Qb{g,h}: Not to get into details, all of these methods mean essentially giving up a physical host NIC (or NF) for the guest, so the host doesn't use it any longer. These will not work in your case, because you only have one NIC on the host.

In short, since you have a small IP range, bridging is your best bet.

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