6.4.c Implement and troubleshoot netflow

6.4.c [i] Netflow v5, v9

Netflow is a feature that was introduced on Cisco routers that give the ability to collect IP network traffic as it enters or exits an interface . By analyzing the data that is provided by Netflow a network administrator can determine things such as the source and destination of the traffic, class of service, and the cause of congestion. Netflow consists of three components : flow caching, Flow Collector, and Data Analyzer.

A network flow can be defined in many ways. Cisco stanfollowing 7 values:

Ingress interface (SNMP ifIndex, can change upon reload)

Source IP address

Destination IP address

IP protocol

Source port for UDP or TCP, 0 for other protocols

Destination port for UDP or TCP, type and code for ICMP, or 0 for other protocols

IP Type of Service

The traditional show command for NetFlow is show ip cache flow also available are two forms of top talker commands. If the show ip cache flow command output shows same SrcIf (source interface ) and DstIf (destination interface), that would be indicative of a routing loop.

Adam, Paul (2014-07-12). All-in-One CCIE V5 Written Exam Guide (Kindle Locations 6169-6171).  . Kindle Edition.

http://en.wikipedia.org/wiki/NetFlow