Multiple Network Adapters in iSCSI or iSER Configuration

If your host has more than one physical network adapter for iSCSI or iSER, you can use the adapters for multipathing.

You can use multiple physical adapters in a single or multiple switch configurations.

In the multiple switch configuration, you designate a separate vSphere switch for each virtual-to-physical adapter pair.

Figure 1. 1:1 Adapter Mapping on Separate vSphere Standard Switches

An alternative is to add all NICs and VMkernel adapters to the single vSphere switch. The number of VMkernel adapters must correspond to the number of physical adapters on the vSphere Standard switch. The single switch configuration is not appropriate for iSER because iSER does not support NIC teaming.

Figure 2. 1:1 Adapter Mapping on a Single vSphere Standard Switch

For that type of configuration, you must override the default network setup and make sure that each VMkernel adapter maps to only one corresponding active physical adapter, as the table indicates.

VMkernel Adapter (vmk#)	Physical Network Adapter (vmnic#)
vmk1 (iSCSI1)	Active Adapters vmnic1 Unused Adapters vmnic2
vmk2 (iSCSI2)	Active Adapters vmnic2 Unused Adapters vmnic1

You can also use distributed switches. For more information about vSphere distributed switches and how to change the default network policy, see the vSphere Networking documentation.

The following considerations apply when you use multiple physical adapters:

• Physical network adapters must be on the same subnet as the storage system they connect to.
• (Applies only to iSCSI and not to iSER) If you use separate vSphere switches, you must connect them to different IP subnets. Otherwise, VMkernel adapters might experience connectivity problems and the host fails to discover the LUNs.
• The single switch configuration is not appropriate for iSER because iSER does not support NIC teaming.

Do not use port binding when any of the following conditions exist:

• Array target iSCSI ports are in a different broadcast domain and IP subnet.
• VMkernel adapters used for iSCSI connectivity exist in different broadcast domains, IP subnets, or use different virtual switches.
  Note: In iSER configurations, the VMkernel adapters used for iSER connectivity cannot be used for converged traffic. The VMkernel adapters that you created to enable connectivity between the ESXi host with iSER and the iSER target must be used only for iSER traffic.