Why 100G Isn’t Dead — And Why 2026 Is the Year Smart Networks Stop Chasing 400G

If you listen to vendor roadmaps and conference keynotes, you’d think anything below 400G belongs in a museum. But step into real networks in 2026 — service providers, regional ISPs, enterprise data centers, hybrid-cloud edges — and a very different reality emerges.

100G is not dead. In fact, for many operators, it’s still the smartest speed they can deploy.

The push toward 400G has been driven more by roadmap pressure and marketing momentum than by actual operational need. And in 2026, the gap between what’s possible and what makes sense is wider than ever.

The Economics Still Favor 100G

Let’s start with cost, because it hasn’t magically gone away. While 400G optics pricing has improved, the total cost of ownership remains materially higher — transceivers, power draw, cooling, and chassis compatibility all add up.

100G optics are mature, abundant, and operationally boring in the best possible way. LR4, ER4, and ZR-lite modules are widely available, interoperability is well understood, and failure rates are predictable. Spares strategies are simpler. Troubleshooting is familiar.

For most operators running metro, regional, or hybrid environments, 100G still delivers the best cost-per-bit without forcing architectural tradeoffs.

Power and Cooling Are the Real Constraints

Bandwidth doesn’t exist in isolation. In 2026, power and cooling are first-order design constraints. 400G line cards and optics consume significantly more power per port. Multiply that across a chassis or a facility and the ripple effects are immediate — denser power feeds, hotter racks, more aggressive cooling, and higher operating costs. Many data centers simply don’t have the headroom to absorb that jump without expensive infrastructure upgrades. 100G platforms, by contrast, fit comfortably into existing power envelopes. They allow operators to scale capacity without triggering a parallel project to redesign their facilities.

AI Traffic Still Doesn’t Mean 400G Everywhere

AI continues to dominate infrastructure conversations, but the traffic patterns haven’t magically become uniform. Training clusters generate massive internal east-west traffic, but upstream connectivity often aggregates cleanly. Inference workloads are bursty, not constant. Replication, backup, and synchronization traffic can be engineered and scheduled. Blanket 400G upgrades are rarely necessary. Thoughtful aggregation using 100G links, paired with traffic engineering and capacity planning, handles most AI-driven demand without overspending.

100G Remains the Sweet Spot for Transitional Architectures

Most networks are transitional by nature. Real-world environments still look like this:

• 10G at the edge and legacy systems
• 40G and 100G in aggregation
• Selective high-capacity uplinks where they are truly justified

100G fits perfectly into this reality. It provides meaningful headroom, clean aggregation, and flexibility without locking operators into a single architectural bet too early.

Extending Hardware Life Is a Feature, Not a Failure

There is nothing outdated about running proven hardware efficiently. Well-designed 100G platforms can deliver years of reliable service. Extending that lifecycle frees capital for areas that actually move the needle — automation, security, observability, redundancy, and operational resilience.

Which Direction Will You Choose?

400G absolutely has its place. Hyperscale cores, ultra-dense fabrics, and specialized environments benefit from it. But treating it as the default answer in 2026 is disconnected from how most networks actually operate. 100G isn’t dead. It’s stable, economical, power-efficient, and aligned with real-world growth.

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