12日 7月 2016

CentOS 7: Bridge interface

This article will describe creating bridge interface of ethernet. This makes that other machines in network can connect to virtual machines on KVM via network.

1 Install bridge-utils package

Install bridge-utils package before creating bridge. 

$ sudo yum install -y bridge-utils

2 Network interfaces of before creating bridge

Network interfaces of before creating bridge is as below. 

$ ifconfig
eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.11.92  netmask 255.255.255.0  broadcast 192.168.11.255
        inet6 fe80::5054:ff:fe86:9b9a  prefixlen 64  scopeid 0x20<link>
        ether 52:54:00:86:9b:9a  txqueuelen 1000  (Ethernet)
        RX packets 106  bytes 13910 (13.5 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 101  bytes 13430 (13.1 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
        inet 127.0.0.1  netmask 255.0.0.0
        inet6 ::1  prefixlen 128  scopeid 0x10<host>
        loop  txqueuelen 0  (Local Loopback)
        RX packets 4  bytes 340 (340.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 4  bytes 340 (340.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

3 Create bridge

ifcfg-eth0 before creating bridge is as below. 

$ cat /etc/sysconfig/network-scripts/ifcfg-eth0
TYPE="Ethernet"
BOOTPROTO="dhcp"
DEFROUTE="yes"
PEERDNS="yes"
PEERROUTES="yes"
IPV4_FAILURE_FATAL="no"
IPV6INIT="yes"
IPV6_AUTOCONF="yes"
IPV6_DEFROUTE="yes"
IPV6_PEERDNS="yes"
IPV6_PEERROUTES="yes"
IPV6_FAILURE_FATAL="no"
NAME="eth0"
UUID="e7765049-e76f-4dc5-8347-db5d4c7b0c8d"
DEVICE="eth0"
ONBOOT="yes"

Copy ifcfg-eth0 to ifcfg-br0. Modify ifcfg-br0 as below.

  • Make TYPE to Bridge.
  • Erase UUID.
  • Make NAME and DEVICE to br0. 
$ cat /etc/sysconfig/network-scripts/ifcfg-br0
TYPE="Bridge"
BOOTPROTO="dhcp"
DEFROUTE="yes"
PEERDNS="yes"
PEERROUTES="yes"
IPV4_FAILURE_FATAL="no"
IPV6INIT="yes"
IPV6_AUTOCONF="yes"
IPV6_DEFROUTE="yes"
IPV6_PEERDNS="yes"
IPV6_PEERROUTES="yes"
IPV6_FAILURE_FATAL="no"
NAME="br0"
DEVICE="br0"
ONBOOT="yes"

Create new ifcfg-eth0.

  • Make HWADDR to 52:54:00:86:9b:9a which is displayed by ifconfig.
  • Make BRIDGE to br0. 
$ cat /etc/sysconfig/network-scripts/ifcfg-eth0
TYPE="Ethernet"
HWADDR="52:54:00:86:9b:9a"
NAME="eth0"
DEVICE="eth0"
ONBOOT="yes"
BRIDGE="br0"

Restart network service. 

$ sudo systemct restart network

4 Network interfaces of after creating bridge

br0 which has the same MAC address with eth0 is created. IP address is assigned to br0. 

$ ifconfig
br0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.11.92  netmask 255.255.255.0  broadcast 192.168.11.255
        inet6 fe80::5054:ff:fe86:9b9a  prefixlen 64  scopeid 0x20<link>
        ether 52:54:00:86:9b:9a  txqueuelen 0  (Ethernet)
        RX packets 35  bytes 2924 (2.8 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 45  bytes 6341 (6.1 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        ether 52:54:00:86:9b:9a  txqueuelen 1000  (Ethernet)
        RX packets 796  bytes 75769 (73.9 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 502  bytes 79165 (77.3 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
        inet 127.0.0.1  netmask 255.0.0.0
        inet6 ::1  prefixlen 128  scopeid 0x10<host>
        loop  txqueuelen 0  (Local Loopback)
        RX packets 12  bytes 1020 (1020.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 12  bytes 1020 (1020.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
カテゴリ： centos-7, 201607, en, bridge