Which 25G SFP28 Module Should You Choose for Your Data Center?

25G SFP28: The Data Center Server Standard Since 2022

SFP28 (SFP 25) is the standard 25 Gigabit Ethernet transceiver for connecting servers to leaf ToR switches in modern data centers. 25G has replaced 10G as the server access speed for three reasons: the same form factor as SFP+ (compatibility with existing ports), 2.5× more bandwidth for a 30% cost premium, and native compatibility with 100G QSFP28 through 4×25G breakout.

In 2026, 80% of new enterprise servers feature dual-port 25G NICs (Intel E810, Mellanox ConnectX-6/7, Broadcom). Hyperconverged VMs (VMware vSAN, Nutanix) and Kubernetes clusters require 25G for storage and replication. 10G is reaching end of life for server access.

25G SFP28 Variants

25GBASE-SR: Multimode for Intra-DC Links

• Reach: 70m over OM3, 100m over OM4.
• Connector: duplex LC (2 fibers).
• Cisco: SFP-25G-SR-S. OPTINOC price: ~€300 excl. VAT.
• Juniper: JNP-SFP-25G-SR. Price: ~€280 excl. VAT.
• Mellanox/NVIDIA: MMS1V00-WM. Price: ~€260 excl. VAT. Compatible with Cisco/Juniper through multi-vendor coding.
• Use case: server ↔ leaf ToR, the #1 scenario in modern data centers.

25GBASE-LR: Long-Range Single-Mode

• Reach: 10km over OS2 single-mode fiber.
• Cisco: SFP-25G-LR-S. OPTINOC price: ~€600 excl. VAT.
• Use case: 25G DCI (rare, usually 100G), inter-building campus links.

25GBASE-CU (DAC): The Most Widely Used Option for Intra-Rack Links

• SFP-25G-CU1M (Cisco): 1m 25G SFP28 DAC. Price: ~€60 excl. VAT.
• SFP-25G-CU3M: 3m 25G SFP28 DAC. Price: ~€80 excl. VAT.
• SFP-25G-CU5M: 5m 25G SFP28 DAC. Price: ~€120 excl. VAT.
• Use case: server ↔ leaf ToR within the same rack. This is the dominant connection in spine-leaf data centers.

25GBASE-AOC: For Short Inter-Rack Links

• SFP-25G-AOC3M: 3m 25G AOC. Price: ~€120 excl. VAT.
• SFP-25G-AOC10M: 10m 25G AOC. Price: ~€200 excl. VAT.

100G QSFP28 → 4× 25G SFP28 Breakout

Modern spine-leaf architecture relies heavily on breakout connectivity: each 100G QSFP28 port on the spine is split into 4× 25G SFP28 connections for 4 servers. A 32× 100G spine switch can connect 128 servers through breakout.

• QSFP-4SFP25G-CU3M (Cisco): QSFP28 → 4× SFP28 breakout DAC, 3m. Price: ~€200 excl. VAT.
• QSFP-100G-AOC-4×25G-10M: 10m breakout AOC. Price: ~€400 excl. VAT.
• Switch configuration: on Nexus, interface breakout module X port Y map 25g-4x. On QFX, set chassis fpc X pic Y port Z channel-speed 25g.

25G Data Center Sizing

• 100 servers, 2× 25G NICs per server (dual-homing) = 200× 25G links.
• 4-8 leaf switches (Nexus 93180YC-FX or QFX5120-48Y), each with 48× 25G = capacity of 192-384 ports.
• Modules: ~200× SFP28 SR or DAC (leaf ↔ server) + ~40× QSFP28 SR4 (leaf ↔ spine).
• Optics budget: ~€60-80K excl. VAT with DACs used for most links, ~€120-150K excl. VAT for an all-fiber deployment.

OPTINOC Recommendations

For a new data center: use 25G SFP28 DACs for 80% of server links (intra-rack) and SFP28 SR fiber for the remaining 20% (inter-rack >5m). OPTINOC supplies Cisco, Juniper, and Mellanox SFP28 modules with manufacturer warranties. Volume discounts are available for orders of 50 modules or more.