You don’t need a six-figure budget to see what’s eating your bandwidth. If you have a router or switch that exports NetFlow, IPFIX, sFlow, or jFlow, you’re already sitting on a goldmine of traffic data. The only missing piece is a free NetFlow monitor to collect and analyze it.
On pfSense/OPNsense: Services > NetFlow > Enable + set collector IP. On Ubiquiti UniFi: System > Advanced > NetFlow Export (IP + Port 2055). Before you build a whole stack, point your router’s NetFlow export to a laptop running ntopng in a Docker container : free netflow monitor
The security investigation tools. You can drill from “High UDP traffic” straight into a flow grid, apply a filter for “Deny” actions, and pivot to a geo-map. No other free tool matches its threat-hunting workflow. You don’t need a six-figure budget to see
flow monitor MY_MONITOR record netflow ipv4 original-input exporter MY_EXPORTER On pfSense/OPNsense: Services > NetFlow > Enable +
interface GigabitEthernet0/1 ip flow ingress ip flow egress flow exporter MY_EXPORTER destination 192.168.1.100 (Your monitor’s IP) transport udp 2055 source Loopback0
The community edition caps at 1 million active flows . That’s fine for branch offices or labs, but not a core data center. 3. ELK Stack (Elasticsearch, Logstash, Kibana) + ElastiFlow Best for: DIY warriors who want unlimited scalability.
It runs best on a dedicated VM (Windows or Linux). The interface is powerful but has a 2010-era learning curve. 2. ntopng (Community Edition) Best for: Real-time visibility and edge monitoring.