I had to start using a dummy interface in my server to make it portable, like a demo in-a-box. Every time that I’ve tried to disconnect it and use other network. I had to make a lot of changes to my configuration: very messy.
Basically, I will tell you how to bridge your dummy interface in centos7. I recommend to disable “NetworkManager” service before anything.
First step is create a dummy interface inside /etc/modprobe.d folder:
[root@box01 ~]# cat /etc/modprobe.d/dummy.conf install dummy /sbin/modprobe --ignore-install dummy; /sbin/ip link set name ethdummy1 dev dummy0 [root@box01 ~]# cat /etc/modules-load.d/dummy.conf # Load dummy.ko at boot dummy [root@box01 ~]# cat /etc/sysconfig/network-scripts/ifcfg-ethdummy1 NAME=ethdummy1 DEVICE=ethdummy1 MACADDR=00:22:22:ff:ff:ff IPADDR=10.10.10.1 NETMASK=255.255.255.0 ONBOOT=yes TYPE=Ethernet NM_CONTROLLED=no
After reboot, check if you dummy is there like I did here:
[root@box01 ~]# ifconfig ethdummy1 ethdummy1: flags=195<UP,BROADCAST,RUNNING,NOARP> mtu 1500 inet 10.10.10.1 netmask 255.255.255.0 broadcast 10.10.10.255 ether 00:22:22:ff:ff:ff txqueuelen 0 (Ethernet)
If you want more details on how you we did until here, you should check out this forum thread: Permanent dummy interface
Now it’s time to turn your dummy into a bridge. Remember the most important value are ONBOOT, BRIDGE, DEVICE
Also, I will create a bridge called 0 connected to this dummy interface.
I’ll bridge ethdummy to bridge0:
[root@box01 ~]# cat /etc/sysconfig/network-scripts/ifcfg-ethdummy1 NAME=ethdummy1 DEVICE=ethdummy1 #MACADDR=00:22:22:ff:ff:ff #IPADDR=10.10.10.1 #NETMASK=255.255.255.0 ONBOOT=yes #TYPE=Ethernet NM_CONTROLLED=no BRIDGE=bridge0 [root@box01 ~]# cat /etc/sysconfig/network-scripts/ifcfg-bridge0 DEVICE="bridge0" ONBOOT="yes" TYPE=Bridge BOOTPROTO=static IPADDR=10.10.10.1 NETMASK=255.255.255.0
Restart network services. My case I used “service network restart”
And let’s check this out.
[root@box01 ~]# brctl show bridge name bridge id STP enabled interfaces bridge0 8000.002222ffffff no ethdummy1
Some Important Notes:
Don’t forget to use iptables to translate IPs and get Internet access from your VMs connected to this new bridge (servers need to use bridge0 IP as the default gateway: 10.10.10.1)
# You need to translate your IPs thru eth0 # eth0 is the interface connected to the Network iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE