Network+ Exam
Netflow Data
October 29, 2025
- #network+
Netflow Data
full packet capture or netflow data can be used to check on network full packet capture will take up too much space.
most orgs will use netflow for flow aynalasya
flow aynalasya - recording metada about stats about network performance. capture info about the data flow vs the actual data.
netflow and flow aynalis provide detailed metadaa. flow aynalis highlights trends and patterns.
normally have visualiation to see patterns easy.
NetFlow - a cisco developed means of reporting network flow info to a structured database. defines traffic flow based on packets that share the same charactristics ex. same sourse and dest ip .
network protocol interface, ip version type.
Zeek - hybrid tool that passivly monitors, logs entire packet when it detects something that is interesting. performes normilization and puts it as JSON.
MRTG - multi router traffic grapher. used to rcreate graphs to show network traffic flows going through network interfaces on different routers.
📊 NetFlow & Flow Data
🔑 Full Packet Capture vs NetFlow
- Full Packet Capture
- Records the entire payload of every packet.
- Very detailed, but consumes huge storage.
- Used in forensics, deep inspection.
- NetFlow (Flow Data)
- Collects metadata only (not payload).
- Developed by Cisco.
- Defines a “flow” as packets with same:
- Source & Destination IP
- Source & Destination Port
- Protocol, Interface, IP version, ToS
- More efficient for long-term monitoring & trend analysis.
📈 Flow Analysis
- Records metadata & statistics about network traffic.
- Useful for:
- Bandwidth usage.
- Identifying top talkers (hosts using most traffic).
- Detecting anomalies (DDoS, scans, unusual spikes).
- Visualization tools (e.g., NfSen, ntopng, MRTG) help spot patterns quickly.
🛠️ Tools
- NetFlow → Cisco-originated, but industry-wide standard.
- Zeek (formerly Bro)
- Hybrid tool: passively monitors, logs metadata.
- Captures full packets only when something interesting is detected.
- Outputs normalized logs (often JSON).
- Used in SOCs for security monitoring.
- MRTG (Multi Router Traffic Grapher)
- Graphs network flows via SNMP polling.
- Often used for traffic visualization over time.
✅ Exam Tips
- NetFlow = metadata only, not payload.
- Flow analysis = trends, anomalies, bandwidth patterns.
- Packet capture = detailed forensics, but storage heavy.
- Zeek = intelligent packet + flow hybrid tool.
- MRTG = visual graphs of router/switch traffic.
⚡ Sample Question:
“Which technology is most commonly used to analyze long-term trends in bandwidth usage while minimizing storage requirements?”
→ NetFlow (flow analysis)