Tag: macvlan

How to run QEMU full virtualization with MacVTap networking using NetworkManager under CentOS 8

In addition to the previously presented article on the subject Howto do QEMU full virtualization with MacVTap networking this one shows how to run a QEMU virtual machine with a MAcVTap device in bridge mode on the host server configured only by using the NetworkManager cli – nmcli.

It is worth mentioning the MacVTap is a virtual bridge, which will make the host and the guest device show up directly on the host switch. So when using QEMU, the guest virtualized system will be as if it is connected to the host switch with one limitation – the host and guest cannot communicate with each other. The IPs of the host won’t be reachable from the guest, so NAT (masquerade) between the host and guest is not possible with this setup. Still, if the NAT server is on another server or a real IP is planned for the guest, MacVTap is the right functionality to use with the QEMU guest system.

Summary

  1. Add MacVTap device in bridge mode with name macvtap0.
  2. Install QEMU.
  3. Create QEMU local disk.
  4. Run a QEMU virtual server.

STEP 1) Add MacVTap device in bridge mode with name macvtap0

[root@srv ~]# nmcli connection add type macvlan dev enp0s3 mode bridge tap yes ifname macvtap0 con-name macvtap0 ip4 0.0.0.0/24
Connection 'macvtap0' (7a5ef04c-ea98-4642-ac5d-4239f715f631) successfully added.
[root@srv ~]# nmcli con
NAME      UUID                                  TYPE      DEVICE   
enp0s3    09497bbf-da59-42b7-a72c-d69369760b36  ethernet  enp0s3   
macvtap0  7a5ef04c-ea98-4642-ac5d-4239f715f631  macvlan   macvtap0

First, create a MacVTap device with the name macvtap0 in bridge mode with the network interface enp0s3 a and a connection with the name macvtap0. The IP is set to manual mode.
More detailed information on how to create and add MacVTap device with the NetworkManager here – Create MacVTap device using NetworkManager nmcli under CentOS 8

STEP 2) Install QEMU.

Install the QEMU virtual tools under CentOS 8 Stream. At present, the QEMU version is 6.2, which is pretty new.
Keep on reading!

gentoo network interface with hyphen in the name

Using the OpenRC (i.e. init system) and network names with special symbols like hyphen in the name may lead to errors of “command not found” and “No such file or directory”

The hyphen in the network interface name must be replaced in the configuration file with an underline and the init name file should be with the hyphen.

Proper configuration for network interface name with hyphen mv-eth0

  • In the configuration file /etc/conf.d/net: 
    config_mv_eth0="
192.168.0.202/24
"
routes_mv_eth0="
default via 192.168.0.1
"
  • The network interface init file is with hyphen: 
    root@srv /etc/init.d # ln -s net.lo net.mv-eth0

And starting the network is successful:

root@srv ~ # /etc/init.d/net.mv-eth0 start
 * Caching service dependencies ...                                                                                                                                                     [ ok ]
 * Bringing up interface mv-eth0
 *   Caching network module dependencies
 *   192.168.0.202/24 ...                                                                                                                                                               [ ok ]
 *   Adding routes
 *     default via 192.168.0.1 ...                                                                                                                                                      [ ok ]
 *   Waiting for tentative IPv6 addresses to complete DAD (5 seconds) ..

Virtualization software may include to the network interface name not so typical alphabets. For example, systemd-nspawn will give name to the guest’s macvlan network with mv-{host_network_name} and iv-{host_network_name} for ipvlan.

Wrong configuration with a hyphen in the network interface name.

The configuration file /etc/conf.d/net:

config_mv-eth0="
192.168.0.202/24
"
routes_mv-eth0="
default via 192.168.0.1
"

Starting the network with such configuration will result in multiple errors:

root@srv ~ # /etc/init.d # /etc/init.d/net.mv-eth0 start
 * Caching service dependencies ...
/etc/init.d/../conf.d/net: line 3: config_mv-eth0=
192.168.0.202/24
: No such file or directory
/etc/init.d/../conf.d/net: line 6: $'routes_mv-eth0=\ndefault via 192.168.0.1\n': command not found
/etc/init.d/../conf.d/net: line 3: config_mv-eth0=
192.168.0.202/24
: No such file or directory
/etc/init.d/../conf.d/net: line 6: $'routes_mv-eth0=\ndefault via 192.168.0.1\n': command not found                                                                                  [ ok ]
/etc/init.d/../conf.d/net: line 3: config_mv-eth0=
192.168.0.202/24
: No such file or directory
/etc/init.d/../conf.d/net: line 6: $'routes_mv-eth0=\ndefault via 192.168.0.1\n': command not found
 * net.mv-eth0: error loading /etc/init.d/../conf.d/net
 * ERROR: net.mv-eth0 failed to start