NetFlow Collector
Setting up Netflow Collectors on Cisco Routers for PRTG
Using the NetFlow protocol you can monitor the bandwidth usage of all packets going through a router. For each flow of data the router sends a netflow packet with connection and bandwidth information to a monitoring system running PRTG. In PRTG you must create a Netflow Collector that accepts these packets and does the accounting.
The advantage of using NetFlow is that it only requires little CPU load on the router itself (e.g. 10.000 active flows create about 7% additional CPU load, 45.000 active flows account for about 20% additional CPU load, see Cisco's performance white paper) and also on the machine running PRTG, especially much less than a Packet Sniffing sensor.
Configure the NetFlow protocol on the router to send NetFlow packets to the computer running PRTG
- (Purchase and) install Netflow Collector License (also works with trial license)
- Configure a Netflow collector in PRTG
- Create one new NetFlow sensor for each IP or protocol to be monitored and apply a filter based on the IP or protocol for each item you want to monitor
- Or: If you do not need long term accounting data for each PC and only want to know the current and recent traffic by IP or protocol, you can create just one NetFlow sensor and enable the Toplist feature based on IP or protocol.
You must edit your router's setup and save it as new startup configuration:
- Log into the router
- run "enable" command giving you admin access
- run "configure" command
More information on setting up NetfFlow for router monitoring for Cisco devices can be found here.