[Network](EN) Network bonding active-backup mode fail_over_mac option

About fail_over_mac option in network bonding active-backup mode


Environment and Prerequisite

  • CentOS 7.7.1908
  • Bash shell(/bin/bash)
  • Network bonding


fail_over_mac option

About fail_over_mac option


fail_over_mac option types

  • none or 0 : (Default) This setting disables fail_over_mac and sets all of the bond and slave interfaces to the same MAC address. Usually first slave’s MAC address is allocated to all bond and slave interfaces.
  • active or 1 : The bond interface’s MAC address is always the MAC address of the active slave interface. If the active slave interface is changed during a failover, the bond interface’s MAC address is then changed to match the new active slave’s MAC address.
  • follow or 2 : The bond interface’s MAC address is fixed(Usually first slave’s MAC address is allocated) and it gives its MAC address to newly active slave interface. If the slave is changed during a failover, the active slave will get the MAC address of the bond interface and the formerly active slave interface receives the newly active slave’s MAC address.


fail_over_mac option examples

Example running environment

  • Example bonding setting is in (Ref) Bonding Setting
  • Host OS : Mac OS
  • Guest OS : CentOS 7.7.1908
  • Hypervisor : VirtualBox


none or 0 option example

  • Default option
  • fail_over_mac=0
  • In VirtualBox environment, it is not work well.
[root@centos-client ~]# cat /etc/sysconfig/network-scripts/ifcfg-bond0 | grep fail_over_mac
BONDING_OPTS="mode=1 miimon=100 fail_over_mac=0"
  • bond0’s and slaves’(enp0s8 and enp0s9) MAC addresses are same.
[root@centos-client ~]# ip link show
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: enp0s3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP mode DEFAULT group default qlen 1000
    link/ether 08:00:27:2b:04:6e brd ff:ff:ff:ff:ff:ff
3: enp0s8: <BROADCAST,MULTICAST,SLAVE,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast master bond0 state UP mode DEFAULT group default qlen 1000
    link/ether 08:00:27:e8:26:58 brd ff:ff:ff:ff:ff:ff
4: enp0s9: <BROADCAST,MULTICAST,SLAVE,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast master bond0 state UP mode DEFAULT group default qlen 1000
    link/ether 08:00:27:e8:26:58 brd ff:ff:ff:ff:ff:ff
8: bond0: <BROADCAST,MULTICAST,MASTER,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP mode DEFAULT group default qlen 1000
    link/ether 08:00:27:e8:26:58 brd ff:ff:ff:ff:ff:ff


active or 1 option example

  • fail_over_mac=1
[root@centos-client ~]# cat /etc/sysconfig/network-scripts/ifcfg-bond0 | grep fail_over_mac
BONDING_OPTS="mode=1 miimon=100 fail_over_mac=1"
  • bond0’s MAC address and first slave’s(enp0s8) MAC address are same.
[root@centos-client ~]# ip link show
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: enp0s3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP mode DEFAULT group default qlen 1000
    link/ether 08:00:27:2b:04:6e brd ff:ff:ff:ff:ff:ff
3: enp0s8: <BROADCAST,MULTICAST,SLAVE,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast master bond0 state UP mode DEFAULT group default qlen 1000
    link/ether 08:00:27:e8:26:58 brd ff:ff:ff:ff:ff:ff
4: enp0s9: <BROADCAST,MULTICAST,SLAVE,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast master bond0 state UP mode DEFAULT group default qlen 1000
    link/ether 08:00:27:27:a9:2d brd ff:ff:ff:ff:ff:ff
9: bond0: <BROADCAST,MULTICAST,MASTER,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP mode DEFAULT group default qlen 1000
    link/ether 08:00:27:e8:26:58 brd ff:ff:ff:ff:ff:ff
  • Link down enp0s8 interface
ip link set dev enp0s8 down
  • bond0’s MAC address is changed to enp0s9’s MAC address.
[root@centos-client ~]# ip link show
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: enp0s3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP mode DEFAULT group default qlen 1000
    link/ether 08:00:27:2b:04:6e brd ff:ff:ff:ff:ff:ff
3: enp0s8: <BROADCAST,MULTICAST,SLAVE> mtu 1500 qdisc pfifo_fast master bond0 state DOWN mode DEFAULT group default qlen 1000
    link/ether 08:00:27:e8:26:58 brd ff:ff:ff:ff:ff:ff
4: enp0s9: <BROADCAST,MULTICAST,SLAVE,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast master bond0 state UP mode DEFAULT group default qlen 1000
    link/ether 08:00:27:27:a9:2d brd ff:ff:ff:ff:ff:ff
9: bond0: <BROADCAST,MULTICAST,MASTER,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP mode DEFAULT group default qlen 1000
    link/ether 08:00:27:27:a9:2d brd ff:ff:ff:ff:ff:ff


follow or 2 option example

  • fail_over_mac=2
  • In VirtualBox environment, it is not work well.
[root@centos-client ~]# cat /etc/sysconfig/network-scripts/ifcfg-bond0 | grep fail_over_mac
BONDING_OPTS="mode=1 miimon=100 fail_over_mac=2"
  • bond0’s MAC address and first slave’s(enp0s8) MAC address are same.
[root@centos-client ~]# ip link show
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: enp0s3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP mode DEFAULT group default qlen 1000
    link/ether 08:00:27:2b:04:6e brd ff:ff:ff:ff:ff:ff
3: enp0s8: <BROADCAST,MULTICAST,SLAVE,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast master bond0 state UP mode DEFAULT group default qlen 1000
    link/ether 08:00:27:e8:26:58 brd ff:ff:ff:ff:ff:ff
4: enp0s9: <BROADCAST,MULTICAST,SLAVE,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast master bond0 state UP mode DEFAULT group default qlen 1000
    link/ether 08:00:27:27:a9:2d brd ff:ff:ff:ff:ff:ff
10: bond0: <BROADCAST,MULTICAST,MASTER,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP mode DEFAULT group default qlen 1000
    link/ether 08:00:27:e8:26:58 brd ff:ff:ff:ff:ff:ff
  • Link down enp0s8 interface
ip link set dev enp0s8 down
  • bond0’s MAC address is same as before.
  • bond0’s MAC address is allocated to newly active slave(enp0s9)
  • enp0s9’s previous MAC address is moved to enp0s8’s MAC address which is failed.
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: enp0s3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP mode DEFAULT group default qlen 1000
    link/ether 08:00:27:2b:04:6e brd ff:ff:ff:ff:ff:ff
3: enp0s8: <BROADCAST,MULTICAST,SLAVE> mtu 1500 qdisc pfifo_fast master bond0 state DOWN mode DEFAULT group default qlen 1000
    link/ether 08:00:27:27:a9:2d brd ff:ff:ff:ff:ff:ff
4: enp0s9: <BROADCAST,MULTICAST,SLAVE,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast master bond0 state UP mode DEFAULT group default qlen 1000
    link/ether 08:00:27:e8:26:58 brd ff:ff:ff:ff:ff:ff
10: bond0: <BROADCAST,MULTICAST,MASTER,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP mode DEFAULT group default qlen 1000
    link/ether 08:00:27:e8:26:58 brd ff:ff:ff:ff:ff:ff


(Ref) Bonding Setting

  • Basic bonding settings are like below.

Interfaces

  • Bonding Interface : bond0
  • Slave Interfaces : enp0s8, enp0s9

bond0

  • /etc/sysconfig/network-scripts/ifcfg-bond0
  • IPADDR and PREFIX could be different.
  • fail_over_mac can set be from 0 to 2.
TYPE=Bond
BOOTPROTO=static
DEFROUTE=no
NAME=bond0
DEVICE=bond0
ONBOOT=yes
PREFIX=24
IPADDR=192.168.99.101
BONDING_OPTS="mode=1 miimon=100 fail_over_mac=1"

enp0s8, enp0s9

  • /etc/sysconfig/network-scripts/ifcfg-enp0s8
NAME=enp0s8
DEVICE=enp0s8
TYPE=Ethernet
BOOTPROTO=none
ONBOOT=yes
MASTER=bond0
SLAVE=yes
  • /etc/sysconfig/network-scripts/ifcfg-enp0s9
NAME=enp0s9
DEVICE=enp0s9
TYPE=Ethernet
BOOTPROTO=none
ONBOOT=yes
MASTER=bond0
SLAVE=yes


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