u/Eagle_TW

Hi all,
I’ve recently been deep-diving into SFP module hardware architectures and Linux network driver source code. I've been tracing what happens when a physical layer failure occurs—such as an optical fiber snap or an internal transceiver hardware fault (TX_FAULT).

While I can clearly see how the low-level Linux kernel driver (drivers/net/phy/sfp.c) handles the physical pin interrupts and handles the internal state machine transitions to drop the interface link, I have a big-picture architectural question about the cascading impacts on the rest of the network stack.

When an SFP link drops out of nowhere, it obviously ripples upward. For example:

• Layer 2: Spanning Tree Protocol (STP/RSTP) must recalculate the topology, LLDP needs to tear down neighbor mappings and update its MIB, and LACP must instantly shift traffic away from the dead port.

I have two core questions for the network architects and firmware engineers here:

1. Where does the responsibility lie? How much of this error handling and cross-protocol signaling is natively handled by the standard Linux kernel, versus how much must be explicitly implemented, tuned, and glued together by a network product designer or NOS (Network Operating System) developer?
2. Is there a standard specification? Is there an industry-standard framework or RFC that comprehensively maps out exactly how physical transceiver faults must propagate through Layer 2, 3, 4, and above to ensure deterministic high-availability? Or is it mostly up to proprietary vendor implementation details?

Hi there,
Recently, I am learning SFP Module and borrow the SFP module from my friends.
By using command i2cdetect -y 104, I found only 0x50 respond.
However, 0x51 does not respond.

Also, there is another SFP Module detect 0x50-0x53.
By reading the data from 0x51-0x53, the information are all empty(0xFF).

About these two cases, anyone has same experience or understand why this happened?