Creating N/w Bridge on CentOS

Hi,

Simple steps for creating bridge on CentOS.

What is bridge and why to use it : In brief There are two ways for giving n/w access to your VM's
      1. NAT : This is bare minimum default, this allows your VM to use Internet but not n/w in which host is, so good for Home use or single machine not so for Office / mulitple machine.
      2. Bridge: As name suggest this will be link for NAT + Host N/w , allowing VM to have n/w ip in range of host.
       If info is not enough will write another blog for that now how to do it.

   First Setup up Gateway as host  i.e.
[root@centos2 ~]# cat /etc/sysconfig/network
NETWORKING=yes
HOSTNAME=centos2
GATEWAY=br0

   Next Step Remove IP details from Eth0 and add another line Bridge=br0

[root@centos2 ~]# cat /etc/sysconfig/network-scripts/ifcfg-eth0

DEVICE=eth0

HWADDR=00:22:4d:ab:ee:61

TYPE=Ethernet

UUID=d455705f-633e-4d5f-b78a-1272c8238c66

ONBOOT=yes

NM_CONTROLLED=yes

BOOTPROTO=none

#IPADDR=192.168.32.52

#NETMASK=255.255.252.0

#DNS2=8.8.8.8

#GATEWAY=192.168.35.254

#DNS1=192.168.32.10

IPV6INIT=no

USERCTL=no

BRIDGE=br0

    Now put IP details in ifcfg-bro with Bridge details

root@centos2 ~]# cat /etc/sysconfig/network-scripts/ifcfg-br0

IPADDR=192.168.32.52

NETMASK=255.255.252.0

DNS2=8.8.8.8

GATEWAY=192.168.35.254

DNS1=192.168.32.10

DEVICE="br0"

NM_CONTROLLED="yes"

ONBOOT=yes

TYPE=Bridge

BOOTPROTO=none

DEFROUTE=yes

IPV4_FAILURE_FATAL=yes

IPV6INIT=no

NAME="System br0"

Hold you breath and restart network

If everything is good you should have n/w access back 

Verify same by brctl show

[root@centos2 ~]# brctl show

bridge name     bridge id               STP enabled     interfaces

br0             8000.00224dabee61       no              eth0

That's it your done