KVM Bridget Network to VM

I’m using Ubuntu 20.04, so all the manipulations are going to be made with netplan.

Also, I’m using singe ordered IPs, not subnets, so I can also order virtual MAC address for each of the IPs. Otherwise, you might want to look into routing options.

This is my original netplan once after OS is installed on my dedicated server. You can find it under /etc/netplan/

ShellScript

### Hetzner Online GmbH installimage
network:
  version: 2
  renderer: networkd
  ethernets:
    enp41s0:
      addresses:
        - X1.X1.X1.X1/32
        - X6:X6:X6:X6::X6/64
      routes:
        - on-link: true
          to: 0.0.0.0/0
          via: Y1.Y1.Y1.Y1
      gateway6: Y16::1
      nameservers:
        addresses:
          - 185.12.64.1
          - 2a01:4ff:ff00::add:2
          - 185.12.64.2
          - 2a01:4ff:ff00::add:1

We are switching it to a bridget network, so VMs can use the bridge with its own IPs to be accessible over SSH protocol.

ShellScript

network:
  version: 2
  renderer: networkd
  ethernets:
    enp41s0:
      dhcp4: no
      dhcp6: no
  bridges:
    br0:
      interfaces: [enp41s0]
      dhcp4: no
      dhcp6: no
      addresses:
        - X1.X1.X1.X1/32
        - X6:X6:X6:X6::X6/64
      routes:
        - on-link: true
          to: 0.0.0.0/0
          via: Y1.Y1.Y1.Y1
      gateway6: Y16::1
      nameservers:
        addresses:
          - 185.12.64.1
          - 2a01:4ff:ff00::add:2
          - 185.12.64.2
          - 2a01:4ff:ff00::add:1
      parameters:
        stp: true
        forward-delay: 4

So, for the interface enp41s0 we disable DHCP, and set up the br0 bridge with the same settings.

Then use one or a conjunction of these commands to apply the settings

ShellScript

netplan generate
netplan try
netplan apply

Next, we need to edit VM settings to use that bridge and virtual MAC address

ShellScript

virsh edit $VM_NAME

And change interface part to look like this

TOML

    <interface type='bridge'>
      <mac address='AA:AA:AA:AA:AA:AA'/>
      <source bridge='br0'/>
      <model type='virtio'/>
      <address type='pci' domain='0x0000' bus='0x01' slot='0x00' function='0x0'/>
    </interface>

Finally, update VM’s netplan. Login into VM

ShellScript

virsh console $VM_NAME
cd /etc/netplan
ls
nano 50-cloud-init.yaml

And this is what I’ve set up

ShellScript

network:
  version: 2
  renderer: networkd
  ethernets:
    enp1s0:
      addresses:
        - X2.X2.X2.X2/32
      routes:
        - to: 0.0.0.0/0
          via: Y2.Y2.Y2.Y2
          on-link: true
      nameservers:
        addresses:
          - 185.12.64.1
          - 2a01:4ff:ff00::add:2
          - 185.12.64.2
          - 2a01:4ff:ff00::add:1

That’s it, reboot everything is it should be working.

This is how to allow SSH access

ShellScript

apt install openssh-server
systemctl status ssh
ufw allow ssh

To allow root access over SSH

ShellScript

nano /etc/ssh/sshd_config

And set PermitRootLogin yes.

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