I have reboot the switch connects to primary slave, eth2. After boot up, the active slave becomes eth1-02. Does anyone understand why the primary slave: eth2 not take up as primary? I guess it has preempt feature.

cat /proc/net/bonding/bond2
Ethernet Channel Bonding Driver: v3.2.4 (January 28, 2008)

Bonding Mode: fault-tolerance (active-backup)
Primary Slave: eth2
Currently Active Slave: eth1-02
MII Status: up
MII Polling Interval (ms): 100
Up Delay (ms): 200
Down Delay (ms): 200

Slave Interface: eth1-02
MII Status: up
Link Failure Count: 0
Permanent HW addr: 00:1c:7f:69:d3:3e

Slave Interface: eth2
MII Status: up
Link Failure Count: 3
Permanent HW addr: 00:1c:7f:83:54:4f