A bonding's primary setting in /etc/sysconfig/network-scripts/ifcfg-bond0 is not effective

Issue

A bonding's primary setting in /etc/sysconfig/network-scripts/ifcfg-bond0 is not effective.

Setting BONDING_OPTS as below, you may see "Primary Slave: None" on /proc/net/bonding/bond0.

For example:

     # grep BONDING_OPTS   /etc/sysconfig/network-scripts/ifcfg-bond0
     BONDING_OPTS='mode=1 miimon=100 primary=eth0'

     # cat /proc/net/bonding/bond0
     Bonding Mode: fault-tolerance (active-backup)
     Primary Slave: None          <----- here
     Currently Active Slave: eth3
     MII Status: up
     MII Polling Interval (ms): 100
     Up Delay (ms): 0
     Down Delay (ms): 0

     Slave Interface: eth3
     MII Status: up
     Link Failure Count: 0
     Permanent HW addr: XX:XX:XX:XX:XX:XX

     Slave Interface: eth0
     MII Status: up
     Link Failure Count: 0
     Permanent HW addr: XX:XX:XX:XX:XX:XX