active-backup mode is configured in Red Hat Enterprise Linux 5 but the bond is not failing over Instead it is rebooting the box

Issue

We have created a Linux bond using two interfaces eth0 and eth4 in active-backup mode but the bond is not failing over when the active interface went down. Instead it is rebooting the box.

Feb  2 16:36:07 oradevap7 kernel: bonding: bond0: Warning: the permanent HWaddr of eth0 - 68:B5:99:C3:82:F0 - is still in use by bond0. Set the HWaddr of eth0 to a different address to avoid conflicts.
Feb  2 16:36:07 oradevap7 kernel: bonding: bond0: making interface eth4 the new active one.
Feb  2 16:36:07 oradevap7 kernel: bonding: bond0: link status definitely down for interface eth4, disabling it
Feb  2 16:36:07 oradevap7 kernel: bonding: bond0: now running without any active interface !
Feb  2 16:36:07 oradevap7 kernel: bonding: bond0: Removing slave eth4
Feb  2 16:36:07 oradevap7 kernel: bonding: bond0: releasing active interface eth4
Feb  2 16:36:07 oradevap7 kernel: bonding: bond0: removing ARP target 10.1.12.1.