NetFlow Analyzer shows valuable information about traffic and bandwidth being utilized on an interface. Reports are displayed about traffic based on volume, speed, utilization and packets and you can also see the source, destination and conversations pertaining to the traffic. All this information is shown on an IN and OUT basis.
One might wonder what the IN and OUT information for different report means. The reports on traffic IN shows the traffic that came into the interface and OUT shows the traffic that went out of the interface. That was simple enough but what about source, destination and conversations IN and OUT?
This too is very easy to understand and to explain this, we will make use of a small scenario. Consider a router with two interfaces, one connected to the LAN and the other connected to the WAN. Here, traffic exchange is taking place between the IP Addresses 126.96.36.199 which lies on the Internet and 188.8.131.52 which is in the local network.
When looking at reports for the WAN interface, the Source tab shows you the source of all traffic passing through this interface. Here, Source IN shows the source IP Addresses of the traffic that came into the network through the WAN interface (from the Internet in this case) and Source OUT shows the the source IP Addresses of the traffic that went OUT of this interface to the internet (in this case, from the LAN).
So, in the scenario, if there is traffic from the IP Address 184.108.40.206 to the LAN IP Address of 220.127.116.11, the Source IN will have the IP Address 18.104.22.168 as this IP Address is the source of traffic that came into the WAN Interface. When the LAN IP 22.214.171.124 sends information back to the public IP Address, the Source OUT will have the IP Address 126.96.36.199 because this is the source of traffic that went OUT of the WAN interface.
The Destination tab in NetFlow Analyzer shows the destination of all traffic that passed through a monitored interface. So, for the WAN interface, Destination IN shows the destination of traffic that came into the interface and Destination OUT shows the destination of traffic that went OUT of the WAN interface.
In the scenario where traffic was from 188.8.131.52 to the LAN IP Address of 184.108.40.206, the Destination IN is 220.127.116.11 because this was the destination of traffic that came into the WAN interface. During the return conversation, the IP Address 18.104.22.168 sends traffic with the destination IP Address as 22.214.171.124 and so this is the Destination OUT.
Coming to the conversation, the traffic exchange from the IP Address 126.96.36.199 to the IP Address 188.8.131.52 is a single conversation and this came into the WAN interface. So, this conversation will form the Conversation IN for the WAN interface. When the local IP Address 184.108.40.206 was sending traffic back to the public IP Address 220.127.116.11, this was a conversation that went out of the WAN interface and so forms the Conversation OUT.
Hope this will have cleared a bit of doubt anyone might have had on traffic being displayed in NetFlow Analyzer. So, all these reports based on IN and OUT should help you know the ins and outs about your network traffic.
Thanks and Regards,
Don Thomas Jacob