MacVTap

MacVTap is a device driver (type="direct") meant to simplify virtualized bridged networking. Typically, this is used in virtualized environments (KVM) to make both the guest and the host show up directly on the switch that the host is connected to and to improve throughput and latencies to external systems.

Example configuration file /etc/libvirt/qemu/:

<interface type="direct"> 
    <mac address=12:34:56:78:9a:bc/> 
    <source dev=private1 mode=bridge/> 
    <model type=virtio/>    
    <driver name=vhost/>  
</interface>

The MAC address field is optional, if omitted, the libvirt daemon (libvirtd) will generate a unique MAC address.

Example Virtual Machine using MacVTap driver in mode bridge:

• virt-install --autostart --check all=on --name YOUR_VM_MACHINE --memory VM_MEMORY --vcpus VM_CPUs --os-variant ubuntu18.04 --cdrom VM_INSTALLATION_MEDIA --disk /path/libvirt/VM_STORAGE_POOL_NAME/YOUR_VM_MACHINE.qcow2 --noautoconsole --wait TIME_TO_WAIT --network type=direct,source=eno111,source_mode=bridge,model=virtio

error: error creating macvtap interface macvtap0@vnet0 (xx:54:00:7d:1c:xx): Device or resource busy

ifconfig -a macvtap0
macvtap0: flags=4419<UP,BROADCAST,RUNNING,PROMISC,MULTICAST>  mtu 9000
        inet6 fe80::5054:ff:feb5:3ef9  prefixlen 64  scopeid 0x20<link>
        ether 52:54:00:b5:3e:f9  txqueuelen 500  (Ethernet)
        RX packets 9669  bytes 936225 (936.2 KB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 9271  bytes 2037747 (2.0 MB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

Activities

1. Learn about different MacVTap modes: https://www.ibm.com/support/knowledgecenter/en/linuxonibm/liaag/wkvm/wkvm_c_net_macvtap.htm#fntarg_1
2. Learn about MacVtap isolation and limitations https://www.ibm.com/support/knowledgecenter/en/linuxonibm/liaag/wkvm/wkvm_c_net_macvtap.htm#fntarg_1
3. Learn about KVM Host Networking Configuration Choices https://www.ibm.com/support/knowledgecenter/en/linuxonibm/liaag/wkvm/wkvm_c_net.htm
4. Read Introduction to Linux interfaces for virtual networking https://developers.redhat.com/blog/2018/10/22/introduction-to-linux-interfaces-for-virtual-networking/

1. Read about trustGuestRxFilters option
2. Learn about MacVTap and VMware https://unix.stackexchange.com/questions/203926/macvtap-on-vmwares-vm

See also

• KVM networking, virsh net, MacVTap, Macvtap logs, virtio, trustGuestRxFilters
• Virsh net: KVM networking, virsh net-info, virsh net-define, virsh net-list, virsh net-edit, virsh net-dhcp-leases, virsh net-start, virsh net-autostart, virsh net-list, KVM networking, /etc/libvirt/qemu/networks/default.xml, MacVTap

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Source: wikiversity