Network interface card (NIC) bonding is another way to add redundancy to Ethernet networks.
With NIC bonding, also known as channel bonding, two or more NICs and their physical connections to the switches are logically bonded together and presented to the IP as a single virtual NIC. If one of the physical connections fails, the traffic is transferred to another NIC without the IP layer or the layers above it knowing about the transfer.
This approach protects against low-level Ethernet failures, such as a faulty NIC or cable, between the host and its local IP switch. Because the redundancy is at a very low level in the protocol stack, the higher layers such as TCP/IP, iSCSI, and device-mapper are not aware that a transfer to a different NIC has taken place. To the IP protocol, the virtual bonded NIC appears as a single physical connection. To iSCSI, it appears as a single connection to each target port.
In short, the iSCSI, device-mapper, and Oracle FS Path Manager (FSPM) layers are not aware of the physical path redundancy provided at the NIC bonding level and do not treat this redundancy as providing multiple paths to the Controller storage controller. Multiple paths created by NIC bonding will not be reported as multiple paths by device-mapper or in the Oracle FS System Manager.