Comment 3 for bug 2000325

# Create a bridge and add two ports

$ sudo ip link add name atx-fabric0 type bridge
$ sudo ip link set up dev atx-fabric0
$ sudo ip tuntap add atx-fabric0i1p1 user $USER group $USER
$ sudo ip tuntap add atx-fabric0i2p1 user $USER group $USER

# create two focal VM images from focal daily server
$ qemu-img create -f qcow2 -b focal-server-cloudimg-amd64.img focal-net1.img 100G
$ qemu-img create -f qcow2 -b focal-server-cloudimg-amd64.img focal-net2.img 100G

# create cloud-init seed

$ cat >user-data <<EOF
#cloud-config
password: passw0rd
chpasswd: { expire: False }
ssh_pwauth: True
ssh_import_id: lp:raharper
EOF
$ echo "i-abcdefg" > meta-data
$ cloud-localds seed.img user-data meta-data

# Launch VM1 (need sudo for bridge access)

BOOT=focal-net1.img
SEED=seed.img
sudo qemu-system-x86_64 -smp 2 -m 2048 --enable-kvm \
  -global pc35.no_floppy=1 \
  -name "${1}" \
  -drive id=disk0,if=none,format=qcow2,file=${BOOT} \
  -device virtio-blk-pci,drive=disk0,bootindex=0 \
  -drive id=cdrom0,if=none,media=cdrom,file=$SEED \
  -device virtio-blk-pci,drive=cdrom0,bootindex=1 \
  -netdev user,id=net0,hostfwd=tcp::22222-:22 \
  -device e1000,bootindex=2,netdev=net0,mac=52:54:00:a2:34:c0 \
  -netdev tap,id=net1,ifname=atx-fabric0i1p1 \
  -device virtio-net,bootindex=4,netdev=net1,mac=b8:38:61:bc:60:f5 \
  -nographic \
  -object rng-random,filename=/dev/urandom,id=rng0 \
  -device virtio-rng-pci,rng=rng0 \
  -serial mon:stdio

# Login and replace netplan config
cat > 50-cloud-init-vm1.yaml << EOF
network:
  version: 2
  ethernets:
    ens5:
      match:
        macaddress: "52:54:00:a2:34:c0"
      accept-ra: false
      dhcp4: true
      dhcp6: false
      mtu: 1500
    eth2-1:
      optional: true
      match:
        macaddress: b8:38:61:bc:60:f5
      set-name: eth2-1
      accept-ra: false
      dhcp4: false
      dhcp6: false
      mtu: 1500
      addresses:
      - 6.1.6.1/24
      - 2006:1:6::1/116
      routes:
      - from: 6.1.6.1
        scope: link
        to: 6.1.6.254
      - from: 2006:1:6::1
        scope: link
        to: 2006:1:6::254
      - to: default
        via: 2006:1:6::254
        metric: 32
      - to: default
        via: 6.1.6.254
        metric: 32
    eth2-2:
      match:
        macaddress: b8:38:61:bc:60:f6
      set-name: eth2-2
      accept-ra: false
      dhcp4: false
      dhcp6: false
      mtu: 1500
EOF
scp -P 22222 50-cloud-init-vm1.yaml ubuntu@localhost:
ssh -P 22222 'sudo cp /home/ubuntu/50-cloud-init-vm1.yaml /etc/netplan/50-cloud-init.yaml'
ssh -P 22222 'sudo netplan apply'

# Launch VM2 (need sudo for bridge access)

BOOT=focal-net2.img
SEED=seed.img
sudo qemu-system-x86_64 -smp 2 -m 1024 --enable-kvm \
  -global pc35.no_floppy=1 \
  -name "${1}" \
  -drive id=disk0,if=none,format=qcow2,file=${BOOT} \
  -device virtio-blk-pci,drive=disk0,bootindex=0 \
  -drive id=cdrom0,if=none,media=cdrom,file=$SEED \
  -device virtio-blk-pci,drive=cdrom0,bootindex=1 \
  -netdev user,id=net0,hostfwd=tcp::22223-:22 \
  -device e1000,bootindex=2,netdev=net0,mac=52:54:00:ef:88:a2 \
  -netdev tap,id=net1,ifname=atx-fabric0i2p1 \
  -device virtio-net,bootindex=4,netdev=net1,mac=b8:38:61:bc:60:f6 \
  -nographic \
  -object rng-random,filename=/dev/urandom,id=rng0 \
  -device virtio-rng-pci,rng=rng0 \
  -serial mon:stdio

# Login and replace netplan config
cat > 50-cloud-init-vm2.yaml << EOF
network:
  version: 2
  ethernets:
    ens5:
      match:
        macaddress: "52:54:00:ef:88:a2"
      accept-ra: false
      dhcp4: true
      dhcp6: false
      mtu: 1500
    eth2-1:
      match:
        macaddress: b8:38:61:bc:60:f5
      set-name: eth2-1
      accept-ra: false
      dhcp4: false
      dhcp6: false
      mtu: 1500
    eth2-2:
      optional: true
      match:
        macaddress: b8:38:61:bc:60:f6
      set-name: eth2-2
      accept-ra: false
      dhcp4: false
      dhcp6: false
      mtu: 1500
      addresses:
      - 6.1.6.1/24
      - 2006:1:6::1/116
      routes:
      - from: 6.1.6.1
        scope: link
        to: 6.1.6.254
      - from: 2006:1:6::1
        scope: link
        to: 2006:1:6::254
      - to: default
        via: 2006:1:6::254
        metric: 32
      - to: default
        via: 6.1.6.254
        metric: 32
EOF

scp -P 22222 50-cloud-init-vm1.yaml ubuntu@localhost:
ssh -P 22222 'sudo cp /home/ubuntu/50-cloud-init-vm1.yaml /etc/netplan/50-cloud-init.yaml'
ssh -P 22222 'sudo netplan apply'