AddOn Cisco GLC-SX-MM Compatible SFP Transceiver - SFP (mini-GBIC) transceiver module - 1GbE - 1000Base-SX - LC multi-mode - up to 550 m - 850 nm - for Cisco 38XX, ASA 55XX, Catalyst ESS9300, Integrated Services Router 11XX

Product Overview

AI-generated summary

At £36.34 ex-VAT for a 1GbE SX SFP, this looks like solid budget territory—*if* you’ve already got multimode infrastructure in place. The use-case is pretty straightforward: short-to-medium runs over OM2/OM3 fibre where 850nm SX optics make sense. For most UK SMB/enterprise “we just need the link to come up” jobs—patching a switch, swapping a failed transceiver, or stocking spares for older Cisco gear—this is the kind of cost-effective replacement that won’t eat your maintenance budget.

That said, I’d be a bit cautious if you’re doing anything mission-critical or picky about optics behaviour. AddOn-compatible modules can be fine, but your real risk isn’t the nominal performance—it’s compatibility quirks with specific Cisco firmware and whether the platform accepts the module cleanly without weird errors or limitations. If your switches/routers are known to be tolerant, you’ll likely be happy; if you’re in a tighter environment (older Cisco models, strict monitoring/alerts, or you can’t risk “unsupported” warnings), I’d test one first or stick to Cisco-branded optics.

Who should buy: teams maintaining 38xx/ASA 55xx/Catalyst ESS9300/ISR 11xx setups with existing multimode fibre who want a cheaper spare. Who should not: anyone needing guaranteed vendor-identical behaviour across firmware or working over single-mode/longer distances where SX isn’t the right fit.