Free ((new)) Netflow Collector -

: The network device (router or switch) that generates flow records.

While Graylog is primarily a log management platform, it has excellent capabilities for ingesting NetFlow data.

NetFlow is a network protocol developed by Cisco for collecting IP traffic information and monitoring network traffic. It is a powerful tool for network administrators to understand traffic patterns, bandwidth usage, and security threats. There are many commercial NetFlow collectors available, but there are also excellent free and open-source options.

The Best Free NetFlow Collectors: 2026 Guide to Network Visibility free netflow collector

"Our bandwidth bill has tripled," she said, sliding a printout across the table. "Find out who’s downloading the Library of Congress."

We resurrected NfSen for a legacy "quick-look" interface, but the real magic was Grafana . We connected Grafana to ClickHouse using a custom plugin. Suddenly, we had real-time dashboards: Sankey diagrams of traffic between subnets, pie charts of egress cost by customer ID, and a terrifying heatmap of port scans.

This was the secret weapon. We abandoned PostgreSQL. ClickHouse is a columnar database built for analytics. It chews through billions of NetFlow records like a woodchipper. Sarah configured an aggregating merge tree to pre-calculate top talkers, protocols, and ASNs. : The network device (router or switch) that

For those who prefer a high-performance, scalable solution, GoFlow2 is a modern favorite in the networking community.

Visibility is everything in network management. Without it, you’re just guessing why the bandwidth is spiking or where that suspicious traffic is coming from. While enterprise-grade solutions exist, you can gain deep insights using a .

Highly scalable and completely free with no device limits. 3. Scrutinizer (Free Version) It is a powerful tool for network administrators

Includes support for Cisco NBAR, IPFIX, and detailed reporting on bandwidth usage. 2. GoFlow2 (Open Source)

We had the usual tools: SNMP (Simple Network Management Protocol) gave us graphs of how much traffic—fat, wiggly lines showing utilization at 95%. But it couldn't tell us who or what . Was it a customer's misconfigured backup? A compromised VM mining crypto? Or just someone streaming 4K cat videos to the breakroom TV?