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How to manage the Network Bridge for KVM.

Posted on July 14, 2023 by nexonhost

How To Manage The Network Bridge For KVM

This guide shows you how to manage the Network Bridge for KVM in Virtualizor.
Virtualizor will create a viifbr0 bridge.
viifbr0 assumes eth0 as the Network Device and detects the IP, Netmask, GATEWAY from :

/etc/sysconfig/network-scripts/ifcfg-eth0
or
/etc/network/interfaces

In the event you have a network device (network interface) other than eth0, e.g. eth1, then you can configure Virtualizor to use eth1 as the Network interface to create the bridge.

 

Network Interface

You can change these settings any time from the Virtualizor Admin Panel -> Configuration -> Slave Settings. The following is a screenshot of the available settings :

image

Note:

By default, eth0 will be assumed as the Network Interface. To tell Virtualizor to use anything other than that, please submit it here.

Managing The Bridge

Virtualizor will create a viifbr0 bridge.

Restart Command :

root> service virtnetwork restart

Start Command :

root> service virtnetwork start

Stop Command :

root> service virtnetwork stop

 

Making The Bridge Permanent

You can make the bridge a permanent one so that whenever the OS is started, it will start with the bridge as soon as the network is created.
This guide presumes the network interface is eth0 and OS is CentOS.

Note:

You will need bridge-utils package installed on your server Backup ifcfg-eth0

 

Backup ifcfg-eth0

The contents of /etc/sysconfig/network-scripts/ifcfg-eth0 will look something like the following :

root# cat /etc/sysconfig/network-scripts/ifcfg-eth0
DEVICE=eth0 
BOOTPROTO=static 
TYPE=Ethernet 
HWADDR=00:25:90:98:35:90 
IPADDR=10.0.0.93 
NETMASK=255.255.255.0 
GATEWAY=10.0.0.1 
IPV6INIT=yes 
IPV6ADDR=2607:f0d0:1002:0011:0000:0000:0000:0002
IPV6_DEFAULTGW=2607:f0d0:1002:0011:0000:0000:0000:0001
ONBOOT=yes

Make a copy of it :

root# cp /etc/sysconfig/network-scripts/ifcfg-eth0 /etc/sysconfig/network-scripts/ifcfg-eth0.bak

 

Create the Bridge File

root# vi /etc/sysconfig/network-scripts/ifcfg-viifbr0

You will need to copy some parts of ifcfg-eth0 to ifcfg-viifbr0 :

DEVICE=viifbr0 
TYPE=Bridge 
BOOTPROTO=static 
IPADDR=10.0.0.93 
NETMASK=255.255.255.0 
GATEWAY=10.0.0.1 
ONBOOT=yes 
IPV6INIT=yes 
IPV6ADDR=2607:f0d0:1002:0011:0000:0000:0000:0002
IPV6_DEFAULTGW=2607:f0d0:1002:0011:0000:0000:0000:0001

Now save the file.

 

Edit the ifcfg-eth0 File

root# vi /etc/sysconfig/network-scripts/ifcfg-eth0

It should look like the following :

DEVICE=eth0
HWADDR=00:25:90:98:35:90 
IPV6INIT=yes 
ONBOOT=yes 
BRIDGE=viifbr0

If your Server belongs to the Hetzner data center, you will also need to rename the interface route file to the bridge’s route file under /etc/sysconfig/network-scripts/ directory.

root#  mv route-eth0 route-viifbr0

Assuming eth0 is the NIC name, you will also need to change the interface name in that route file from eth0 to viifbr0.

root#  mv route6-eth0 route6-viifbr0

Assuming eth0 is the NIC name, you will also need to change the interface name in that route file from eth0 to viifbr0.

 

Restart Network

We are almost setup now. Just make sure everything is correct before you restart the network. After that restart the network :

root#  service network restart

Note:

Virtnetwork will not work anymore and you should restart only with network.

Ubuntu network interface File

Note:

You will need bridge-utils package installed on your server For IPv4 Configuration

root# nano /etc/network/interfaces
# The loopback network interface 
auto lo
iface lo inet loopback 

# Bridge for eth0  
auto viifbr0  
iface viifbr0 inet static   
address 192.168.1.10   
netmask 255.255.255.0   
gateway 192.168.1.1   
dns-nameservers 192.168.1.5    
bridge_ports eth0    
bridge_stp off    
bridge_fd 0    
bridge_maxwait 0

bridge_stp off – is a setting for spanning tree. If you have a possibility for network looks, you may want to turn this on.

bridge_fd 0 – turns off all forwarding delay. If you do not know what this is, you probably do not need it.

bridge_maxwait 0 – is how long the system will wait for the Ethernet ports to come up. Zero is no wait.

For IPv6 Configuration, edit the Following file :

root # vi /etc/sysctl.conf

Add the following line at the end of the file :

net.ipv6.conf.default.disable_ipv6 = 0
net.ipv6.conf.all.disable_ipv6 = 0

Save and exit the file.

The last file we need to edit is the interfaces file under the path  /etc/network/

root # vi /etc/network/interfaces

Append the following lines to the file :

iface viifbr0 inet6 static
pre-up modprobe ipv6
address IPv6-IP-Address
netmask IPv6-NetMask
gateway IPv6-IP-Gateway-Address

 

Restart Network

We are almost set up now. Just make sure everything is correct before you restart the network. After that restart the network :

root# /etc/init.d/networking restart

Note:

Virtnetwork will not work anymore and you should restart only with the network.

Managing Bridge on Ubuntu 18.04 or higher

On Ubuntu 18.04 they have enabled netplans for network interface by default.
Either you can turn off the netplans and use the legacy method (i.e. /etc/network/interfaces) OR configure a Network Bridge as per the following guide :

To configure netplan, save configuration files under /etc/netplan/ with a .yaml extension (e.g. /etc/netplan/config.yaml),
then run sudo netplan apply.
This command parses and applies the configuration to the system.

Configuration written to disk under /etc/netplan/ will persist between reboots.

Note:

You will need the bridge-utils package installed on your server

Example file contents : /etc/netplan/01-netcfg.yaml

For Hetzner servers,

network:
  version: 2
  renderer: networkd
  ethernets:
    ens3:
      dhcp4: no
  bridges:
    viifbr0:
      addresses: 
        - 10.1.3.43/24
        - "2001:cafe:face:beef::dead:dead/64"
      interfaces: [ ens3 ]
      routes:
        - on-link: true
          to: 0.0.0.0/0
          via: 10.1.3.1
      gateway6: fe80::1
      macaddress: 00:16:3e:7f:ae:93
      nameservers:
         addresses:
           - 8.8.8.8
           - 8.8.4.4
           - 2a01:4f8:0:1::add:1010
           - 2a01:4f8:0:1::add:9898

For other servers :

network:
  version: 2
  renderer: networkd
  ethernets:
    ens3:
      dhcp4: no
  bridges:
    viifbr0:
      addresses: 
        - 10.1.3.43/24
        - "2001:cafe:face:beef::dead:dead/64"
      interfaces: [ ens3 ]
      gateway4: 10.1.3.1
      gateway6: "2001:cafe:face:beef::1"
      macaddress: 00:16:3e:7f:ae:93
      nameservers:
         addresses:
           - 8.8.8.8
           - 8.8.4.4
           - 2a01:4f8:0:1::add:1010
           - 2a01:4f8:0:1::add:9898

Netplan network bridge

After making the netplan Network Bridge, please add the interface name to Virtualizor as per the following guide :

Virtualizor Network in KVM