When deploying Ethernet-based storage protocols like iSCSI or NVMe/TCP, establishing a healthy Layer 1 physical connection is the absolute first step. On standard Pure Storage FlashArray controllers (like the //X50 or //X70), the default on-board high-speed ports (ETH2 and ETH3) utilize SFP28 physical cages. These specific ports are hardware-designed to support 10GbE or 25GbE speeds depending on the inserted SFP+ or SFP28 transceiver.

In this scenario, a fundamental physical layer mismatch is occurring. The array ports are attempting to link at 10 Gb/s (using SFP+ optics), but the upstream SAN switch is operating natively at 40 Gb/s (which utilizes a physically larger QSFP+ form factor with four parallel 10G lanes). Auto-negotiation across mismatched optical form factors and lane architectures will almost always fail, resulting in a dead link showing 0 b/s.

An Implementation Engineer cannot magically "force negotiate" a 10G/25G SFP28 port on the array to run at 40G because the physical hardware simply does not support that bandwidth or encoding. Attempting to force the switch side (Option C) will also fail if the physical media doesn't match. The only correct, supported resolution is a hardware intervention: the engineer must replace the transceivers with the appropriate type . Typically, this involves using a QSFP-to-SFP adapter (QSA) on the switch side, or utilizing a specialized 40G-to-4x10G breakout cable to ensure both ends of the fiber are communicating using the exact same light wavelengths, lane counts, and physical port speeds.