StarTech.com Cisco QSFP-40G-CSR4 Compatible QSFP+ Module - 40GBASE-SR4 - 40GbE Multimode Fiber MMF Optic Transceiver - 40GE Gigabit Ethernet QSFP+ - MPO 300m - 850nm - DDM Cisco Firepower, ASR9000, ASR1000

Product Overview

AI-generated summary

At £36 ex-VAT, this StarTech QSFP+ SR4 module is the kind of low-cost, high-sanity option you buy when you already know your fibre links are multimode and you just need 40GbE to work without paying “Cisco tax” for every spare. The fact it’s described as compatible and includes DDM-style monitoring is the real-world win for me: in daily operations, being able to see optics health helps you avoid the slow-burn surprises that pop up when modules are failing or links are marginal. If you’re equipping Cisco kit like ASR/Firepower gear and your network already expects this QSFP+ SR4 behaviour, it’s a sensible budget play.

That said, I wouldn’t buy it blindly. £36 is cheap because it’s not trying to be universal magic—compatibility depends on your exact Cisco platform/firmware expectations, and multimode vs singlemode matters a lot. Also, don’t assume “compatible” means “identical behaviour”: if you’re tight on link margin, MPO polarity/fibre cleanliness, or you’re pushing the upper end of the stated reach, you may end up with intermittent link training issues that cost more time than the module savings. Bottom line: buy it if you’re replacing a like-for-like QSFP+ SR4 optic and you can control/verify your multimode fibre + patching; skip it if you need guaranteed compatibility across mixed hardware/firmwares or you’re not confident about the fibre path.