Using QEMU with the virtio-net Internal Network for Network Simulations

For years I’ve primarily used x86 PCs. With that, VirtualBox had a unique feature called the Internal Network that could be used to isolate VLANs. But more recently I’ve been daily-driving a M3 Pro MacBook Pro on-and-off.

However, VirtualBox on Apple Silicon cannot run MikroTik CHR. While it does run on UTM, UTM doesn’t give me isolated non-DHCP VLANs. Also, attempts at using “bridge” interfaces failed miserably.

The solution? QEMU. I tested this guide on macOS 15 Sequoia but it should also work on Linux, Windows and BSD variants.

The commands for VM 1:

qemu-system-aarch64 \
  -machine virt \
  -cpu cortex-a57 \
  -m 1024 \
  -bios /opt/homebrew/Cellar/qemu/10.0.2_2/share/qemu/edk2-aarch64-code.fd \
  -nographic \
  -drive file=c1.img,format=raw,if=virtio \
  -device virtio-net,netdev=net1 -netdev socket,id=net1,listen=:1234

And VM 2:

qemu-system-aarch64 \
  -machine virt \
  -cpu cortex-a57 \
  -m 1024 \
  -bios /opt/homebrew/Cellar/qemu/10.0.2_2/share/qemu/edk2-aarch64-code.fd \
  -nographic \
  -drive file=c2.img,format=raw,if=virtio \
  -device virtio-net,netdev=net1 -netdev socket,id=net1,connect=:1234

NOTE: These commands are specific for ARM Macs using Homebrew. Linux/BSD systems and x86 Macs (if not emulating ARM64) will have different commands.

The most interesting line on these two VMs is the last line. From VM 1:

-device virtio-net,netdev=net1 -netdev socket,id=net1,listen=:1234

This line sets up a net1 network listening on port 1234.

For the VM 2:

-device virtio-net,netdev=net1 -netdev socket,id=net1,connect=:1234

This connects to VM 1 via port 1234

You can technically repeat these lines for multiple VLANs/interfaces, but haven’t done it (yet).