In this blog I would like to go over how to enable sFlow on Fortigate switches. Supposed we want to configure a Fortigate device to export sFlow, for instance, to a server 10.10.10.10. This server is listening for flow packets on port 2055, and we want a sampling rate of 1 for every 2000 packets.

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There is no doubt that flow technology is revolutionizing network monitoring. In this  NetFlow/J-Flow/IPFIX/sFlow era, there is no need to settle with only knowing utilizations on the network. Besides, little analysis can be done in monitoring bandwidth only anyways.

Scott wrote a blog earlier that made a valid point: “A Network Administrator’s abilities are only as good as his awareness of what happens on his network.” In harmony with that statement, it’s beneficial to have useful tools to be able to collect that traffic information.

Recently, I learned that J-Flow is supported for the Juniper SRX series Gateways. I thought this might be good information for people who want to start monitoring flows on this type of device, especially our NetFlow and sFlow Analyzer users, since it can also process J-Flow packets. Below are some sample commands taken from Juniper’s Knowledge Base which walks you through your J-Flow configuration. Read more »

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Why do you want to know what is going on in the traffic flow of a network?

What’s the point?

Why doesn’t utilization alone cut it?

Network Administrators don’t typically have a lot of time on a day-to-day basis. There is always some fire to fight, some network or user issue that comes up. Most times your juggling more than one issue at a time. So you find yourself spending most of your time trying to keep the network running and the users happy.

A Network Administrator’s abilities are only as good as his awareness of what happens on his network.

Monitoring and maintaining your network traffic and bandwidth utilization used to be an overlooked aspect of your job. But evolution of technology has changed the makeup of networks everywhere and has forced network managers to include Flow analysis and monitoring in their network management strategies.

Network Flow Analysis is the art of studying the traffic on a computer network. It is the  industry-standard method of collecting and recording network traffic. Flow analysis lets you see what types of traffic passed between hosts, without having to reproduce the problem.

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I worked with Brad Reese and some of our internal engineering folks to put this post together on a Free NetFlow Forwarder or NetFlow Duplicator called “The Samplicator”.  Read more »

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How do you know if the NetFlow collector is saving or even getting all of the NetFlow datagrams that are being sent to it or that it is receiving? It is important to know if any flows are missing.

Why do we care?

This is a great question. We care because a loss of flow exports is usually caused by one of three things:

1. The network dropped some packets
2. The router can’t keep up
3. The NetFlow receiver / collector can’t keep up

NetFlow sequence numbers are becoming increasingly important. When building a NetFlow collector it is important that the engine scales while staying accountable. If you look at the NetFlow v9 packet format you will notice something called the package_sequence.

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JFlow is a IP traffic flow sampler technology used by Juniper manufactured routers and switches. JFlow is considered a flow sampler technology much like Sflow, and when enabled on an interface; it allows packets in the input stream to be sampled. As the packets flow through an input stream the router/switch will look at each one, but only records new packets and discards any packets it has already seen.

JFlow is just one of three flow technologies available; among the 3 include Cisco’s Netflow and HP’s Sflow technologies. Each having their own strengths; Netflow records all packets while SFlow will only sample incoming traffic based on the packet ratio defined in the router configuration.

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