FlowViewer

FlowViewer is a network-flow analysis tool for organizations collecting traffic data from their own devices. It is best suited to teams able to run a Unix server and looking for reports, graphs, and ongoing monitoring without a software fee. Its broad analysis toolkit is appealing, but the server requirement should shape the decision.

Overview

FlowViewer provides a dynamic interface to Carnegie Mellon’s SiLK software and also supports the legacy flow-tools collector. Its three components divide the work: FlowViewer produces text reports, FlowGrapher charts traffic, and FlowMonitor tracks filtered traffic over time. That makes it a more complete fit for teams wanting analysis and operational monitoring together than a tool focused on a single view.

FlowViewer supports NetFlow versions 5 and 9, including IPv6. IPFIX and sFlow also appear in its protocol list, so teams should check that their collector and device setup supports the workflow they need.

Key features

Reports and filtering

More than 30 reports and the ability to save reports and filters help analysts revisit recurring questions without recreating each view. Filters cover address, port, interface, autonomous system, TOS, TCP flags, protocol, and next hop. That breadth supports investigation across several common network dimensions, though it is most useful to teams already collecting compatible flow data.

Graphing and monitoring

FlowGrapher plots bits per second, flows per second, and packets per second across a chosen period, giving teams several ways to understand traffic rates. FlowMonitor adds RRD graphs for filtered traffic, with views spanning 24 hours to three years. The long range is useful for tracking patterns over time; teams seeking a live operational view can also use multiple dashboards to let groups such as Security and Operations focus on their own concerns.

Pricing

FlowViewer is free software at free. The trade-off is operational rather than a software charge: it requires a Unix server, whether dedicated or virtual. That makes it attractive to organizations with suitable infrastructure, but less compelling for teams seeking a hosted, turnkey deployment.

Optional paid help covers deployment and know-how. Custom Support costs price on request, billed per hour with a four-hour minimum. Router Netflow Config is $500, paid once for configuration and troubleshooting until the stream reaches the collector. FlowViewer Training costs $500, paid once; a web conference using a live installation is suggested. A full FlowViewer and SiLK installation on a Unix server costs $750, paid once. These services can help teams that want expert assistance, but they add costs beyond the free software.

Platforms

FlowViewer is listed for Linux and the web, and can be installed on a dedicated Unix server or virtual appliance. The deployment model suits teams comfortable maintaining that server environment; it is not a fit for organizations that require a desktop-native or mobile workflow.

Who it's for

FlowViewer makes the most sense for network and operations teams that collect flow data, want saved reports and filters, and value monitoring views that reach back as far as three years. Its distinct reporting, graphing, and monitoring components cover several needs in one free package. Teams without Unix-server capacity, or whose devices and collectors do not match its supported flow workflow, should look elsewhere.

Pros and cons

• Pros: Free software includes text reports, graphing, and long-term monitoring, so teams can cover multiple flow-analysis tasks without a software license.
• Pros: More than 30 reports, reusable filters, and filtering across addresses, ports, interfaces, and other dimensions support repeated investigations.
• Cons: A Unix server is required, adding infrastructure and administration considerations even though the software itself is free.
• Cons: NetFlow v5 and v9 are the stated supported versions; teams using other collection setups should verify compatibility before deployment.

Alternatives

ManageEngine NetFlow Analyzer is worth considering for teams needing broader platform coverage or a choice between a free edition capped at two interfaces and paid editions; its Standard Edition is $172 a month for 10 interfaces.

ntopng is another free-plan option for teams looking for Linux, macOS, Windows, web, or self-hosted platform choices.

Caligare Flow Inspector may suit teams that prefer a free edition with explicit limits—non-commercial use, two devices, 24-hour history, and 250 flows per second—or want a free trial.

Nagios XI is an alternative for teams comparing a free tier limited to seven nodes or 100 services, whichever comes first, with paid options and a free trial.

ElastiFlow offers a free Basic plan with caps of 4,000 records per second and 25 SNMP devices, plus dashboards and ML detections; it may suit teams seeking those published capacity limits and integrations.

nfdump is a free Linux and self-hosted alternative for teams considering a BSD-licensed flow-analysis tool.

Riverbed Aternity is an enterprise offering with custom pricing.

Akvorado is a free alternative developed by Free, a French ISP.

Browse more options in Network Traffic Analysis Software and Bandwidth Monitoring Software.

Verdict

Choose FlowViewer if your organization already collects compatible flow data, can run a Unix server, and wants reports, graphs, and long-range filtered traffic monitoring at no software cost. Its main advantage is the range of analysis in one free tool; look elsewhere if the server requirement or flow-format fit does not suit your environment.