Open vSwitch

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Open vSwitch (OVS) is a multilayer software switch. It is designed to enable massive network automation through programmatic extension, while still supporting standard management interfaces and protocols. Open vSwitch is well suited to function as a virtual switch in VM environments.

Installation

Install the openvswitch package.

Required services and setup

To use ovs-vswitchd, start/enable ovs-vswitchd.service.

ovs-vswitchd.service will also start the ovsdb-server.service which is used for saving the OVS configuration in a database for persistent settings across reboots.

Create a Bridge

$ ovs-vsctl add-br mybridge

Most commands can be reversed with replacing add with del, for example del-br.

Print the newly created bridge with one port with an interface named mybridge. 

$ ovs-vsctl show
e4e95383-2d81-45bd-b411-d289b11405b2
    Bridge mybridge
        Port mybridge
            Interface mybridge
                type: internal

Add physical adapter to the bridge

Get the current active interface and configuration: 

$ ip addr
2: eno1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
    link/ether 52:54:00:91:11:95 brd ff:ff:ff:ff:ff:ff
    inet 192.168.1.10/24 brd 192.168.1.255 scope global dynamic eno1
       valid_lft 82284sec preferred_lft 82284sec
    inet6 fe80::5054:ff:fe91:1195/64 scope link
       valid_lft forever preferred_lft forever

Disable any running automated config, Either 

$ dhcpcd -k eno1 # if dhcpcd is running
$ systemctl stop systemd-networkd.service # for systemd-networkd
$ ip addr del 192.168.1.10/24 dev eno1 #  also remove the current ip configuration

Add physical interface to mybridge: 

$ ovs-vsctl add-port mybridge eno1
Warning: This will loose connectivity on this adapter, ensure you have another way to reach your system.

Print the current setup: 

$ ovs-vsctl show
e4e95383-2d81-45bd-b411-d289b11405b2
    Bridge mybridge
        Port mybridge
            Interface mybridge
                type: internal
        Port eno1
            Interface eno1

Test the config: 

$ dhcpcd mybridge
$ ip addr
2: eno1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel master ovs-system state UP group default qlen 1000
    link/ether 52:54:00:91:11:95 brd ff:ff:ff:ff:ff:ff
    inet6 fe80::5054:ff:fe91:1195/64 scope link
       valid_lft forever preferred_lft forever
3: ovs-system: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN group default qlen 1000
    link/ether 6e:a7:28:66:78:e2 brd ff:ff:ff:ff:ff:ff
4: mybridge: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN group default qlen 1000
    link/ether ba:21:d0:cd:38:4f brd ff:ff:ff:ff:ff:ff
    inet 192.168.1.11/24 brd 192.168.1.255 scope global dynamic noprefixroute mybridge
       valid_lft 86372sec preferred_lft 75572sec
    inet6 fe80::183e:d590:9014:eeb4/64 scope link
       valid_lft forever preferred_lft forever

Make changes persistent over reboots

Open vSwitch will automatically apply any changes made with ovs-commands. But to get it working we need to change some things with systemd-networkd:

First, remove any old configuration for eno1 and bring the interface up during boot. We will also run DHCP on mybridge with the following config: 

/etc/systemd/network/eno1.network
[Match]
Name=eno1
/etc/systemd/network/mybridge.network
[Match]
Name=mybridge

[Network]
DHCP=ipv4

Vlans

Setup trunk with vlan 10 + 20 plus tag untagged traffic to vlan 1 through the physical port: 

$ ovs-vsctl set port eno1 vlan_mode=native-untagged
$ ovs-vsctl set port eno1 tag=1 # tag untagged vlan 1
$ ovs-vsctl set port eno1 trunks=10,20 # allow tagged vlans 10 and 20
Tip:

Do multiple actions in one command with -- as seperator, For example, the above is same as :
$ ovs-vsctl set port eno1 vlan_mode=native-untagged -- set port eno1 tag=1 -- set port eno1 trunks=10,20

Create a new vport1, type internal for use on the host system with vlan 10: 

$ ovs-vsctl add-port mybridge vport1 tag=10 -- set Interface vport1 type=internal
$ dhcpcd vport1 # to test it out!

Virtual ports

ip_forward is needed for virtual ports and support for vm's: 

$ echo 1 > /proc/sys/net/ipv4/ip_forward

Manually create a tuntap interface: 

$ ip tuntap add mode tap vport2

To make both the above changes persistent across reboots: 

/etc/sysctl.conf
net.ipv4.ip_forward = 1
/etc/systemd/network/90-vport2.netdev
[NetDev]
Name=vport2
Kind=tap

Create a new port and tag it vlan 20: 

$ ovs-vsctl add-port mybridge vport2 -- set port vport2 tag=20

vport2 can now be used in libvirt.

See also