** README: Please perform the below operations from a serial console/or direct physical access to the machine.***

1/ Disable Network Manager
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[root@intel network-scripts]# systemctl disable NetworkManager.service 
rm '/etc/systemd/system/network.target.wants/NetworkManager-wait-online.service'
rm '/etc/systemd/system/dbus-org.freedesktop.NetworkManager.service'
rm '/etc/systemd/system/multi-user.target.wants/NetworkManager.service'
[root@intel network-scripts]# 
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2/ Enable classic Network Service
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[root@intel network-scripts]# systemctl enable network.service 
network.service is not a native service, redirecting to /sbin/chkconfig.
Executing /sbin/chkconfig network on
[root@intel network-scripts]# 
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3/ List the contents of the interface file & bridge file
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[root@intel network-scripts]# cat ifcfg-ksdev0 
# Generated by dracut initrd
DEVICE=ksdev0
ONBOOT=yes
NETBOOT=yes
UUID=86bf09b6-00ef-4120-9a9e-ffcdafe78668
DHCPV6C=yes
BOOTPROTO=dhcp
HWADDR="00:13:20:fb:6a:c3"
TYPE=Ethernet
NAME="Boot Disk"
NM_CONTROLLED=no
BRIDGE=br0
[root@intel network-scripts]# 
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[root@intel network-scripts]# cat ifcfg-br0 
DEVICE=br0
ONBOOT=yes
TYPE=Bridge
BOOTPROTO=dhcp
DELAY=0
[root@intel network-scripts]# 
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4/ Stop NetworkManager service
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[root@intel network-scripts]# systemctl stop NetworkManager.service 
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5/ Restart classic network service
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[root@intel network-scripts]# systemctl restart network.service
[ 7805.035599] IPv6: ADDRCONF(NETDEV_UP): ksdev0: link is not ready
[ 7805.046487] device ksdev0 entered promiscuous mode
[ 7805.102669] IPv6: ADDRCONF(NETDEV_UP): br0: link is not ready
[ 7808.651259] e1000e: ksdev0 NIC Link is Up 1000 Mbps Full Duplex, Flow Control: None
[ 7808.660026] IPv6: ADDRCONF(NETDEV_CHANGE): ksdev0: link becomes ready
[ 7808.667399] br0: port 1(ksdev0) entered forwarding state
[ 7808.673435] br0: port 1(ksdev0) entered forwarding state
[ 7808.679571] IPv6: ADDRCONF(NETDEV_CHANGE): br0: link becomes ready
[root@intel network-scripts]# 
[root@intel network-scripts]# 
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6/ Check the unit-file status of network & NetworkManger service
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root@intel network-scripts]# systemctl is-enabled network.service
network.service is not a native service, redirecting to /sbin/chkconfig.
Executing /sbin/chkconfig network --level=5
enabled
[root@intel network-scripts]# 
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[root@intel network-scripts]# systemctl is-enabled NetworkManager.service
disabled
[root@intel network-scripts]#
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[root@intel network-scripts]# systemctl | grep -i network.service
network.service             loaded active running   LSB: Bring up/down networking
[root@intel network-scripts]# 
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7/ List the bridge devices
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[root@intel network-scripts]# brctl show
bridge name	bridge id		STP enabled	interfaces
br0		0080.001320fb6ac3	no		ksdev0
virbr0		8000.52540031df08	yes		virbr0-nic
[root@intel network-scripts]# 
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8/ Your  bridge(br0) will have the IP address , (and your em1 or eth0 interface will lose the IP address - which is expected)

(NOTE: I just masked out IP with 'ww.xx.yy.aaa')
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[root@intel network-scripts]# ifconfig br0
br0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet xx.yy.zz.aaa  netmask 255.255.248.0  broadcast xx.yy.zz.bbb
        inet6 fe80::213:20ff:fefb:6ac3  prefixlen 64  scopeid 0x20<link>
        inet6 aaaa:52:0:102f:213:20ff:fefb:6ac3  prefixlen 64  scopeid 0x0<global>
        ether 01:13:20:fb:6a:c3  txqueuelen 0  (Ethernet)
        RX packets 5285  bytes 327277 (319.6 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 43  bytes 9259 (9.0 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

[root@intel network-scripts]# 
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[root@intel network-scripts]# ifconfig ksdev0
ksdev0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet6 fe80::213:20ff:fefb:6ac3  prefixlen 64  scopeid 0x20<link>
        ether 00:13:20:fb:6a:c3  txqueuelen 1000  (Ethernet)
        RX packets 93749  bytes 7696115 (7.3 MiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 518  bytes 89871 (87.7 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
        device interrupt 20  memory 0xc2700000-c2720000  

[root@intel network-scripts]# 
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