Virtual routing and forwarding (VRF) is a technology included in IP (Internet Protocol) network routers that allows multiple instances of a routing table to exist in a router and work simultaneously. This increases functionality by allowing network paths to be segmented without using multiple devices. Because traffic is automatically segregated, VRF also increases network security and can eliminate the need for encryption and authentication. Internet service providers (ISPs) often take advantage of VRF to create separate virtual private networks (VPNs) for customers; thus the technology is also referred to as VPN routing and forwarding. Read more »

Michael Patterson
Scrutinizer Product Manager
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I love that title. It sounds so dramatic.

I’ve been seeing this issue lately and I think it’s worth talking about, since I can imagine it affects the way you see flows within just about any NetFlow traffic analyzer.

Within a NetFlow v5 packet, there are two rows that define the inbound and the outbound interface for every conversation. Those interface numbers are really just the ifindex interface ID assigned by your router.

The inbound/outbound interface fields are crucial to being able to calculate where your traffic stream is going.

Lets look at a couple screenshots:

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