Used 100G QSFP28 SR4 Transceiver Module

QSFP28 SR4 Specifications and Compatible Systems

Compatible systems: Cisco Nexus 9300/9500 (requires Cisco OUI or disable unsupported-transceiver warning with service unsupported-transceiver), Arista 7280R/7300 series, Dell EMC Z9500/Z9100, Juniper QFX10000, HPE Aruba 8400. Compatibility warning: Third-party QSFP28 SR4 modules will trigger error messages on Cisco Nexus without OUI programming or the service unsupported-transceiver CLI command — the module will still pass traffic but generates persistent error logs that can mask real faults. Use genuine Cisco-branded optics if NOC alerting hygiene matters.

What to Check Before Buying a Used QSFP28 SR4 in 2026

1. DOM optical power readings: Use show interface transceiver (Cisco/Arista) to verify TX power between –7.3 and +2.4 dBm and RX power above –9.5 dBm on all 4 lanes. Any lane outside spec means a degraded VCSEL — reject for production use.
2. Bit error rate test: Run a BERT test over the target fiber run at 25G per lane for 5 minutes. BER >10⁻¹² on any lane indicates a marginal module likely to fail within 6 months under sustained traffic.
3. Physical MPO connector inspection: Use a fiber optic inspection scope (e.g., JDSU FiberChek) on the MPO ferrule. Contamination on >1 fiber pin face increases insertion loss by 0.5–3 dB per lane — a significant link budget hit on 100m OM4 runs.
4. EEPROM vendor ID verification: Read the Vendor Name and OUI from the module EEPROM using ethtool -m <interface> or vendor CLI. Ensure the OUI matches expectations — counterfeit modules with spoofed OUIs from 2020–2023 production runs circulate in the secondary market for Cisco applications.
5. Temperature and voltage telemetry: Under traffic load, module case temperature should stay below 70°C. Modules from data centers without hot/cold aisle containment often show thermal stress patterns — sustained >75°C operation reduces VCSEL life by 30–50%.

Frequently Asked Questions

OEM Cisco QSFP28 SR4 vs. third-party MSA-compatible — is there a real performance difference? No — the IEEE 802.3bm spec is tight enough that compliant MSA modules deliver identical throughput and BER performance. The only meaningful differences: (1) Cisco NX-OS throws unsupported-transceiver errors with third-party optics, (2) Cisco TAC will ask you to swap to OEM optics during troubleshooting. For non-Cisco switches, third-party modules are indistinguishable from OEM.

Can I use QSFP28 SR4 for runs longer than 100m? Not reliably. At 100m on OM4, you're already at the link budget limit.

How long do used QSFP28 transceivers last in production? VCSEL-based transceivers have MTBF of 7–10 years in normal data center environments (ASHRAE Class A1/A2, <27°C). High-temperature environments (>35°C sustained) cut this to 4–6 years. Monitor TX power via DOM monthly — gradual TX power degradation of >0.5 dB/year is the earliest reliable failure predictor.

Are there counterfeit QSFP28 SR4 modules in the secondary market? Yes — particularly counterfeit Cisco-branded modules with correct labeling but substandard VCSELs and weak optical power margins. Buy from vendors who provide DOM readouts and EEPROM dumps as part of the listing. Reject any module where the seller can't provide optical power readings.

Last updated: May 2026. Pricing reflects current 2026 secondary market conditions. Request a quote for current availability.