Ok guys,

I have to create several bridges to test SD-WAN in just one computer. And also avoid me the work to change IP segments every time my box is moving among different places 🙂
My base hots is a Centos7 and I am using it laso as my router. Don’t forget to create routes in your laptop to access all elements. You need to use the following syntax in case of a Mac:

sudo route -n add -net 10.250.250.0/24  192.168.1.113

I want to create a topology like this:

Load the dummy module

Do the following to create 3 dummies interfaces:

modprobe dummy numdummies=3
echo "dummy" > /etc/modules-load.d/dummy.conf
echo "options dummy numdummies=3" > /etc/modprobe.d/dummy.conf

Create the bridges and interfaces

Check out my configuration for this dummies that I will bridge later to core, wan and inet bridges.

[root@box01 ~]# cat /etc/sysconfig/network-scripts/ifcfg-dummy0
DEVICE=dummy0
MACADDR=52:54:00:7e:27:d0
NM_CONTROLLED=no
ONBOOT=yes
TYPE=Ethernet
BRIDGE=core
IPV6INIT=no
[root@box01 ~]# cat /etc/sysconfig/network-scripts/ifcfg-dummy1
DEVICE=dummy1
MACADDR=52:54:00:7e:27:d1
NM_CONTROLLED=no
ONBOOT=yes
TYPE=Ethernet
BRIDGE=wan
IPV6INIT=no
[root@box01 ~]# cat /etc/sysconfig/network-scripts/ifcfg-dummy2
DEVICE=dummy2
MACADDR=52:54:00:7e:27:d2
NM_CONTROLLED=no
ONBOOT=yes
TYPE=Ethernet
BRIDGE=inet
IPV6INIT=no

Finally, I will create the bridges

[root@box01 ~]# cat /etc/sysconfig/network-scripts/ifcfg-core
DEVICE="core"
ONBOOT="yes"
TYPE=Bridge
BOOTPROTO=static
IPADDR=10.10.10.1
NETMASK=255.255.255.0
[root@box01 ~]# cat /etc/sysconfig/network-scripts/ifcfg-wan
DEVICE="wan"
ONBOOT="yes"
TYPE=Bridge
BOOTPROTO=static
IPADDR=10.250.250.1
NETMASK=255.255.255.0
[root@box01 ~]# cat /etc/sysconfig/network-scripts/ifcfg-inet
DEVICE="inet"
ONBOOT="yes"
TYPE=Bridge
BOOTPROTO=static
IPADDR=80.80.80.1
NETMASK=255.255.255.0

Reboot your server and you will get this into your interfaces (use “ip addr” command):

6: dummy0: <BROADCAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc noqueue master core state UNKNOWN 
    link/ether 52:54:00:7e:27:d0 brd ff:ff:ff:ff:ff:ff
7: dummy1: <BROADCAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc noqueue master wan state UNKNOWN 
    link/ether 52:54:00:7e:27:d1 brd ff:ff:ff:ff:ff:ff
8: dummy2: <BROADCAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc noqueue master inet state UNKNOWN 
    link/ether 52:54:00:7e:27:d2 brd ff:ff:ff:ff:ff:ff
9: wlp0s22u1u2: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN qlen 1000
    link/ether 74:da:38:7d:86:81 brd ff:ff:ff:ff:ff:ff
10: core: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP 
    link/ether 52:54:00:7e:27:d0 brd ff:ff:ff:ff:ff:ff
    inet 10.10.10.1/24 brd 10.10.10.255 scope global core
       valid_lft forever preferred_lft forever
11: wan: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP 
    link/ether 52:54:00:7e:27:d1 brd ff:ff:ff:ff:ff:ff
    inet 10.250.250.1/24 brd 10.250.250.255 scope global wan
       valid_lft forever preferred_lft forever
12: inet: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP 
    link/ether 52:54:00:7e:27:d2 brd ff:ff:ff:ff:ff:ff
    inet 80.80.80.1/24 brd 80.80.80.255 scope global inet
       valid_lft forever preferred_lft forever

Connect your virsh domains to those bridges

Easy, check the xml domain file and edit the interface section that way:

    <interface type='bridge'>
      <source bridge='wan'/>
      <target dev='vnet6'/>
      <model type='virtio'/>
      <alias name='net0'/>
    </interface>
    <interface type='bridge'>
      <source bridge='inet'/>
      <target dev='vnet7'/>
      <model type='virtio'/>
      <alias name='net1'/>
    </interface>

Check your bridges and connection that way:

[root@box01 ~]# brctl show
bridge name	bridge id		STP enabled	interfaces
branch01		8000.fe540027b5c5	no		vnet14
							vnet15
							vnet18
							vnet19
							vnet20
							vnet8
branch02		8000.000000000000	no		
core		8000.5254007e27d0	no		dummy0
							vnet0
							vnet10
							vnet11
							vnet3
							vnet4
							vnet5
							vnet9
inet		8000.5254007e27d2	no		dummy2
							vnet13
							vnet17
							vnet2
							vnet7
wan		8000.5254007e27d1	no		dummy1
							vnet1
							vnet12
							vnet16
							vnet6

See ya!