Whats the difference between SNMP and NetFlow?

Traditional SNMP Performance Monitoring
Traditionally customers relied almost exclusively on Simple Network Management Protocol (SNMP) to monitor bandwidth. Although SNMP facilitates capacity planning, it does little to characterize traffic applications and patterns, essential for understanding how well the network supports the business. A more granular understanding of how bandwidth is being used is extremely important in IP networks today. Packet and byte interface counters are useful but understanding which IP addresses are the source and destination of traffic and which applications are generating the traffic is invaluable.

NetFlow Based Network Awareness
The ability to characterize IP traffic and understand how and where it flows is critical for network availability, performance and troubleshooting. Monitoring IP traffic flows facilitates more accurate capacity planning and ensures that resources are used appropriately in support of organizational goals. It helps IT determine where to apply Quality of Service (QoS), optimize resource usage and it plays a vital role in network security to detect Denial-of-Service (DoS) attacks, network-propagated worms, and other undesirable network events.
NetFlow facilitates solutions to many common problems encountered by IT professionals.

• Analyze new applications and their network impact

Identify new application network loads such as VoIP or remote site additions.

• Reduction in peak WAN traffic

Use NetFlow statistics to measure WAN traffic improvement from application-policy changes; understand who is utilizing the network and the network top talkers.

• Troubleshooting and understanding network pain points

Diagnose slow network performance, bandwidth hogs and bandwidth utilization quickly with command line interface or reporting tools.

• Detection of unauthorized WAN traffic

Avoid costly upgrades by identifying the applications causing congestion.

• Security and anomaly detection

NetFlow can be used for anomaly detection and worm diagnosis.

• Validation of QoS parameters

Confirm that appropriate bandwidth has been allocated to each Class of Service (CoS) and that no CoS is over- or under-subscribed.

Ref: https://www.cisco.com/en/US/products/ps ... 6232.shtml