xref: /cloud-hypervisor/docs/macvtap-bridge.md (revision da5fae38141d179d29a7771fdbeff2c4142ca03f)

# Using MACVTAP to Bridge onto Host Network

Cloud Hypervisor supports using a MACVTAP device which is derived from a MACVLAN. Full details of configuring MACVLAN or MACVTAP is out of scope of this document. However the example below indicates how to bridge the guest directly onto the network the host is on. Due to the lack of hairpin mode it not usually possible to reach the guest directly from the host.

```bash
# The MAC address must be attached to the macvtap and be used inside the guest
mac="c2:67:4f:53:29:cb"
# Host network adapter to bridge the guest onto
host_net="eno1"

# Create the macvtap0 as a new virtual MAC associated with the host network
sudo ip link add link "$host_net" name macvtap0 type macvtap
sudo ip link set macvtap0 address "$mac" up
sudo ip link show macvtap0

# A new character device is created for this interface
tapindex=$(< /sys/class/net/macvtap0/ifindex)
tapdevice="/dev/tap$tapindex"

# Ensure that we can access this device
sudo chown "$UID:$UID" "$tapdevice"

# Use --net fd=3 to point to fd 3 which the shell has opened to point to the /dev/tapN device
target/debug/cloud-hypervisor \
	--kernel ~/src/linux/vmlinux \
	--disk path=~/workloads/focal.raw \
	--cpus boot=1 --memory size=512M \
	--cmdline "root=/dev/vda1 console=hvc0" \
    --net fd=3,mac=$mac 3<>$"$tapdevice"
```

As the guest is now connected to the same L2 network as the host you can obtain an IP address based on your host network (potentially including via DHCP)