16.7. Configuring bridges on a network bond to connect virtual machines with the network

Procedure

1. Create a bond interface:

   # nmcli connection add type bond con-name bond0 ifname bond0 bond.options "mode=active-backup"

   This command creates a bond named bond0 that uses the active-backup mode.

2. Assign the Ethernet interfaces to the bond:

   # nmcli connection add type ethernet slave-type bond con-name bond0-port1 ifname enp7s0 master bond0
   # nmcli connection add type ethernet slave-type bond con-name bond0-port2 ifname enp8s0 master bond0

   These commands create profiles for enp7s0 and enp8s0, and add them to the bond0 connection.

3. Configure the IPv4 settings:

   • To use DHCP, no action is required.

   • To set a static IPv4 address, network mask, default gateway, and DNS server to the bond0 connection, enter:

     # nmcli connection modify bond0 ipv4.addresses 192.0.2.1/24 ipv4.gateway 192.0.2.254 ipv4.dns 192.0.2.253 ipv4.dns-search example.com ipv4.method manual

4. Configure the IPv6 settings:

   • To use stateless address autoconfiguration (SLAAC), no action is required.

   • To set a static IPv6 address, network mask, default gateway, and DNS server to the bond0 connection, enter:

     # nmcli connection modify bond0 ipv6.addresses 2001:db8:1::1/64 ipv6.gateway 2001:db8:1::fffe ipv6.dns 2001:db8:1::fffd ipv6.dns-search example.com ipv6.method manual

5. Optional: If you want to set any parameters on the bond ports, use the following command:

   # nmcli connection modify bond0-port1 bond-port.<parameter> <value>

6. Configure that Red Hat Enterprise Linux enables all ports automatically when the bond is enabled:

   # nmcli connection modify bond0 connection.autoconnect-ports 1

7. Activate the bridge:

   # nmcli connection up bond0

Verification

1. Temporarily remove the network cable from the host.

   Note that there is no method to properly test link failure events using software utilities. Tools that deactivate connections, such as nmcli, show only the bonding driver’s ability to handle port configuration changes and not actual link failure events.

2. Display the status of the bond:

   # cat /proc/net/bonding/bond0

Procedure

1. Create a bridge interface:

   # nmcli connection add type bridge con-name br0 ifname br0 ipv4.method disabled ipv6.method disabled

2. Add the bond0 bond to the br0 bridge:

   # nmcli connection modify bond0 master br0

3. Configure that Red Hat Enterprise Linux enables all ports automatically when the bridge is enabled:

   # nmcli connection modify br0 connection.autoconnect-ports 1

4. Reactivate the bridge:

   # nmcli connection up br0

Procedure

1. Create the ~/bond0-bridge.xml file with the following content:

   <network>
   	<name>bond0-bridge</name>
   	<forward mode="bridge" />
   	<bridge name="br0" />
   </network>

2. Use the ~/bond0-bridge.xml file to create a new virtual network in libvirt:

   # virsh net-define ~/bond0-bridge.xml

3. Remove the ~/bond0-bridge.xml file:

   # rm ~/bond0-bridge.xml

4. Start the bond0-bridge virtual network:

   # virsh net-start bond0-bridge

5. Configure the bond0-bridge virtual network to start automatically when the libvirtd service starts:

   # virsh net-autostart bond0-bridge

Procedure

1. To create a new VM and configure it to use the bond0-bridge network, pass the --network network:bond0-bridge option to the virt-install utility when you create the VM:

   # virt-install ... --network network:bond0-bridge

2. To change the network settings of an existing VM:

   1. Connect the VM’s network interface to the bond0-bridge virtual network:

      # virt-xml <example_vm> --edit --network network=bond0-bridge

3. Shut down the VM, and start it again:

   # virsh shutdown <example_vm>
   # virsh start <example_vm>