Netflow Tools May 2026

# Flows per second (FPS) spike nfcapd -p 2055 -w -l /data -T all # Real-time: watch -n 1 'nfdump -R /data -r current -s flows | head' (requires NetFlow v9 + BGP table)

SELECT src_host, sum(bytes) as total_bytes FROM netflow.flows WHERE flow_start > now() - 3600 GROUP BY src_host ORDER BY total_bytes DESC LIMIT 10; | Symptom | Likely Cause | Fix | |---------|--------------|-----| | No flows received | ACL blocking UDP 2055 | show access-list | | Flows show 0 bytes | Sampling rate too high | Reduce sampling-rate | | AS numbers are 0 | BGP table not loaded | ip flow-export bgp-nexthop | | Timestamps wrong | NTP drift | ntp peer on exporter | | High CPU on router | Flow cache too large | ip flow-cache entries 65536 |

set forwarding-options sampling input rate 1000 set forwarding-options sampling family inet output cflowd 192.168.1.100 port 2055 version 5 :

plugins: kafka aggregate: src_host, dst_host, src_port, dst_port, proto, tos, src_as, dst_as kafka_topic: netflow_raw kafka_broker_host: kafka1:9092,kafka2:9092 imt_path: /var/spool/pmacct - Top talkers last hour:

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This guide covers production-grade NetFlow tooling. Start with nfdump for small environments, pmacct + ClickHouse for mid-scale, and GoFlow2 + Kafka for carrier-grade.