Dell M1000e Blade Server and Network Bonding

Hello everyone, I'm having an issue configuring our Dell blade server to use network bonding. I'm running RHEL 6 and configured the bond0 interface with eth2 and eth3 (fiber) with mode 1 (active/backup, actually tried all modes). I see both interfaces but when I unplug one of the network fiber cables, it doesn't failover. But if I pull the IO card out, it fails over. It also works if I down the interface. It's like it doesn't see that the link is down when I unplug the fiber cable. I tried using the option arp_ip_target and it didn't help. Any help is appreciated!

Forgot to mention that the blade server has 2 M8428-k IO cards.

Thanks!
Pete