25G/100G Aggregation Switch: Buying Guide

The Data Center Aggregation Switch: The Spine

In a spine-leaf architecture, the aggregation switch (spine) interconnects all leaf switches. Its 100G or 400G port density determines how many leaf switches—and therefore servers—the fabric can support. A 32× 100G spine can connect 32 leaf switches directly or, when a second spine is added for redundancy, support 64 leaf switches with 4 uplinks each.

The spine does not connect to servers—only to leaf uplinks and, where applicable, super-spine links in a three-tier fabric or DCI links. Its role is to forward packets between leaf switches with the lowest possible latency (<1.5µs) and without oversubscription, as spine switches are non-blocking.

Leading 100G Spine Switches

Cisco Nexus 9336C-FX2

• 36× 40/100G QSFP28, 1U, ~1µs latency.
• 40MB shared buffer.
• Standalone NX-OS or ACI.
• Native VXLAN-EVPN with a BGP control plane.
• OPTINOC price: ~€18,000-22,000 excl. VAT.
• Use case: Spine switch for a fabric with 8-32 100G leaf switches. The Cisco standard.

Cisco Nexus 9364C-GX

• 64× 40/100G QSFP28, 2U, very high density.
• Price: ~€30,000-35,000 excl. VAT.
• Use case: Spine switch for very large data centers with 32-64 leaf switches, or as a super-spine.

Juniper QFX5120-32C

• 32× 40/100G QSFP28, 1U, ~550ns latency (the lowest available).
• Junos OS: Atomic commits and Apstra compatibility.
• OPTINOC price: ~€15,000-18,000 excl. VAT.
• Use case: Juniper alternative to the Nexus 9336, at a 15% lower price.

Aruba CX 8325-32C

• 32× 100G QSFP28, 1U.
• AOS-CX with REST API and VSX MLAG between 2 spine switches.
• OPTINOC price: ~€20,000 excl. VAT.

Next-Generation 400G Spine Switches

Cisco Nexus 9332D-GX2B

• 32× 400G QSFP-DD, 1U.
• Can also operate as 128× 100G using breakout connections.
• Price: ~€45,000-55,000 excl. VAT.
• Use case: 400G spine for hyperscale fabrics or future-ready deployments.

Juniper QFX5130-32CD

• 32× 400G QSFP-DD, 1U, ~800ns latency.
• Price: ~€40,000-48,000 excl. VAT.

Spine-Leaf Sizing

Small DC (8 Leaf Switches)

• 2 Nexus 9336C-FX2 spine switches (32× 100G each).
• 8 93180YC-FX leaf switches, each with 6 100G uplinks to the 2 spine switches = 3 uplinks per spine.
• Oversubscription: 48×25G downlinks / 6×100G uplinks = 2:1. Suitable for conventional workloads.
• Spine-switch budget: ~€40,000 excl. VAT.

Medium-Sized DC (32 Leaf Switches)

• 4 Nexus 9336C-FX2 or QFX5120-32C spine switches.
• 32 leaf switches, each with 4 100G uplinks connected to the 4 spine switches.
• Spine-switch budget: ~€70,000-80,000 excl. VAT.

Large DC (64+ Leaf Switches)

• 4-8 Nexus 9332D-GX2B (400G) or QFX5130-32CD spine switches.
• 64-128 leaf switches with 100G or 400G uplinks.
• Spine-switch budget: €200K-400K excl. VAT.

OPTINOC Recommendations

For 80% of enterprise data centers, choose the Nexus 9336C-FX2 or QFX5120-32C. The Nexus is preferred for Cisco ecosystems, while the QFX is well suited to automation with Apstra and budget-sensitive deployments. For new deployments from 2027 onward, move directly to 400G with the Nexus 9332D-GX2B.