An engineer must connect a Cisco UCS B-Series based system to an existing large storage area network fabric. The deployment must support hardware-based load balancing, prevent Fibre Channel domain ID

Enabling Fibre Channel end-host mode on the Cisco UCS Fabric Interconnect ensures it behaves as an N-Port to the SAN, thus preventing domain ID exhaustion by not merging FC domains. Concurrently, enabling NPIV (N_Port ID Virtualization) on the upstream SAN switch allows the Fabric Interconnect to present multiple virtual HBAs from the blade servers through its physical uplinks, facilitating hardware-based load balancing across multiple links and enabling all blade servers to operate within the same VSAN.

Connecting the fabric interconnect to E Ports on the SAN switch implies that the FI is operating in Fibre Channel switch mode, which would cause domain ID exhaustion by attempting to merge FC domains, contradicting the requirement to prevent it.

Configuring Ethernet end-host automatic load balancing pertains to Ethernet traffic, not Fibre Channel storage traffic, and therefore does not address Fibre Channel domain ID exhaustion or SAN connectivity requirements.

While placing all interfaces that face the fabric interconnects in the same VSAN is a necessary configuration for SAN connectivity, it alone does not provide hardware-based load balancing or prevent Fibre Channel domain ID exhaustion, which are key requirements of the question.