Comment 14 for bug 1041070

This is related to the bonding mode and _not_ a bug. The bonding module will drop duplicate frames received on inactive ports, which is normal behavior. [0] Overall the packets should be getting into the machine without problems since they are received on the active slave. To confirm this do the following

1) Check dropped packets from all interfaces. So if eth0/eth1 are connected to bond0, we may see dropped packets for bond0 and eth0, but not for eth1. This depends on which interface is the active interface. This can be checked using the following:
cat /sys/class/net/bond0/bonding/active_slave

So if the active_slave isn't dropping packets, and the inactive slave is dropping packets this is normal in 'active-backup' mode (or any mode where there is an inactive slave).

2) If we want both interfaces to not drop packets we can use 'all_slaves_active' bonding module parameter [0].
Check:
cat /sys/class/net/bond0/bonding/all_slaves_active, it should default to 0 which means drop frames on the inactive slave.

If we set this to 1, we will no longer drop frames:
echo 1 | sudo tee /sys/class/net/bond0/bonding/all_slaves_active