Yes, netFlow does consume additional memory and CPU resources, therefore, it is important to understand the resources required on your router before enabling NetFlow.
To enable netflow, enter into the interface configuration mode of the specific interface with which you want to enable netflow.In that mode, type the following to enable netflow. (config-if)# ip route-cache flow
No, catalyst 2950 and 2970 doesn't support netflow.For more info on netflow, refer the folllowing link.
The extra CPU load is minimal as the hard work is allready done by CEF which is hardware based. Obviously the Netflow export adds CPU cycles but the export info is done whhen each session ends, not on a regula basis like SNMP so Netflow is much better than SNMP in this respect.
nTop is an open source Netflow collector which makes nice graphs and detects and flags anomolous host behavours. You can browse to it to get results and if you run it on Linux its free.
We are pleased to announce availability of Beta software for 16.6.3. 16.6.3 will be the second rebuild on the 16.6 release train targeted towards Catalyst 9500/9400/9300/3850/3650 switching platforms. We are looking for early feedback from custome...