The NetFlow Advantage: Why SPAN Ports Fall Short

Investment in digital infrastructure is skyrocketing as companies work to improve operational efficiency and keep pace with the amount of digital data being generated. For example, in 2024 alone, the world is expected to generate 1.5 times the amount of digital data it did just two years ago.

For the cybersecurity teams responsible for protecting and monitoring networks, this requires modern solutions designed to perform in a hybrid IT environment. However, many weren’t designed with network security in mind, like having to rely on legacy switch SPAN (Switched Port Analyzer) ports for visibility.

Security operators need to see every connection or they could miss a threat, and that complete visibility starts with the systems and users connected to the network. This blog post explores the comparative advantages of NetFlow over SPAN, so that cybersecurity teams can put their organizations on the right path to cyber resilience.

What Is SPAN and Why Is It Risky?

SPAN ports, also known as Port Mirroring, are specialized ports found on switches or routers. They are designed to replicate selected packets moving through the device and forward them to a designated destination port. This process ensures precise monitoring and analysis of network traffic.

Historically, an engineer would connect a SPAN port directly to intrusion detection systems (IDS) or network monitoring tools. But with today’s modern networks, operators look for a more reliable and secure way to connect security and monitoring solutions, gain visibility, and properly analyze threats and anomalies.

SPAN doesn’t actually do any monitoring, but the risks and expenses linked to SPAN become more prominent as organizations reevaluate their digital infrastructures, posing significant challenges to operations teams responsible for improving cyber resilience.

Reasons for Packet Loss Due to SPAN

One key reason security teams avoid using SPAN is due to packet loss, often occurring in heavy use or oversubscribed ports.

Despite modern networks operating at speeds of 1G, 10G, 40G, or higher, many switches still drop packets at lower speeds, even if the network isn't fully saturated.

	Memory Shortage: Insufficient memory leads to the inability to store and analyze crucial packets.
	PAUSE Frame Attacks: Malicious bad actor activities flood the SPAN disguised as a loopback, hiding bad data and forcing dropped packets.
	Broken CRC: Packets showing broken cyclic redundancy check (CRC) are automatically dropped, missing potential security issues.
	Size Limitations: Frames smaller than 64 bytes or bigger than the configured maximum transmission unit (MTU), are dropped because of an ingress rate limit.

The Advantages of a NetFlow Solution

NetFlow is a feature on most Layer 3 devices, such as routers, firewalls, WiFi Controllers and L3 switches, that captures flows and exports them to an external server for analysis. Unlike SPAN which simply dumps everything it sees on specific ports to the monitoring port, crushing valuable resources, NetFlow provides more structured information at a configurable sampling rate.

Specifically, NetFlow tracks flows—series of packets sharing characteristics like source/destination ports, addresses, protocols, and QoS markings. For instance, IP phone conversations, FTP sessions, and web page views are all considered flows. Any devices using network resources cannot escape being captured by a flow record when designed properly and implemented strategically.

How NetFlow Benefits IT/Cybersecurity Teams

In the context of today's complex and ever-evolving IT environments, the ability to balance detailed network monitoring with efficient resource use makes NetFlow an invaluable solution for achieving a resilient and secure network infrastructure.

NetFlow also offers the visibility traditionally limited to SPAN solutions, without burdening the network.

	Enhanced Network Visibility: NetFlow provides a metadata-based overview of network activity, allowing for a detailed understanding of traffic flow without the need for full packet capture. This visibility is crucial for monitoring and securing network traffic effectively.
	Efficient Problem Solving: The detailed statistics generated from NetFlow data enable IT teams to identify and resolve network issues such as bottlenecks, ensuring optimal network performance.
	Comprehensive Security Posture: When combined with the capabilities of next-generation firewalls, NetFlow offers a powerful solution for protecting against security threats and investigating alerts, enhancing the organization's overall security posture.
	Boosted Efficiency: NetFlow minimizes load and preserves the essential functions of routing and switching traffic, demonstrating its efficiency and utility in maintaining network integrity and performance.

Building Cyber Resilience with NetFlow

As the landscape of cybersecurity threats—ranging from Zero Day attacks and Advanced Persistent Threats to malware and ransomware—continues to evolve, organizations are increasingly recognizing how NetFlow enables operators to reach actionable insights about security incidents swiftly.

Integrating NetFlow with cutting-edge security technologies empowers both Network Operations (NetOps) and Security Operations (SecOps) teams. It not only allows them to monitor network issues effectively but also provides the detailed data necessary to identify the specifics of an incident—who was involved, from where, over what duration, and the actions taken.

By prioritizing complete visibility, organizations can ensure their journey towards digital transformation is secure, resilient and aligned with the highest standards of cybersecurity. For information on how to build a more resilient connected environment or to learn more about the benefits of NetFlow solutions, contact us today at hello@uncommonx.com.